Synthetic Approach to Readily Accessible Benzofuran-Fused BODIPY

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Synthetic Approach to Readily Accessible BenzofuranFused BODIPY as Red-Emitting Laser Dyes José L. Belmonte-Vázquez, Edurne Avellanal-Zaballa, Ernesto Enríquez-Palacios, Luis Cerdán, Ixone Esnal, Jorge Bañuelos, Clarisa Villegas-Gómez, Iñigo Lopez Arbeloa, and Eduardo Peña-Cabrera J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.8b02933 • Publication Date (Web): 31 Jan 2019 Downloaded from http://pubs.acs.org on February 5, 2019

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The Journal of Organic Chemistry

Synthetic Approach to Readily Accessible BenzofuranFused BODIPY as Red-Emitting Laser Dyes José L. Belmonte-Vázquez,† Edurne Avellanal-Zaballa,≠ Ernesto Enríquez-Palacios,† Luis Cerdán,¥ ,¥ Ixone Esnal,≠ Jorge Bañuelos,≠ ,* Clarisa Villegas-Gómez,† Iñigo López Arbeloa,≠ Eduardo Peña-Cabrera†,*

† Departamento

de Química. Universidad de Guanajuato, Noria Alta S/N. Guanajuato, Gto.

Mexico 36050 ≠

Departamento de Química Física. Universidad del País Vasco-EHU, Apartado 644, 48080, Bilbao, Spain. ¥ Instituto

de Química-Física “Rocasolano”, CSIC. Serrano 119, 28006 Madrid, Spain

Email: [email protected], [email protected]

Abstract We took advantage of the chemoselective meso-functionalization 2,3,5,6-tetrabromo-8methylthioBODIPY 6 to prepare a series of 2,3,5,6-tetrabromo-8-arylBODIPY derivatives suitable for SNAr substitution reactions with phenols exclusively at the 3-and 5-positions. Pd(0)-catalyzed intramolecular arylation reaction ensued on the remaining brominated 2- and 6-positions to give a new family of benzofuran-fused BODIPY dyes. This method utilizes readily available starting materials and allows for the preparation of the title compounds with excellent functional group tolerance. Moreover, it was demonstrated that the methodology described herein is amenable for the incorporation of biomolecules. The photophysical and lasing properties of the benzofuran-fused BODIPY dyes were thoroughly analyzed with the aid of electrochemical measurements and quantum mechanical simulations. These dyes show

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bright and intriguing emission (both fluorescence and laser) towards the red edge of the visible spectrum with remarkable tolerance under a strong and continuous irradiation.

Introduction Borondipyrromethenes (BODIPYs)11 (Figure 1), are arguably some of the most versatile fluorophores there are.2 Plenty has been written about their synthesis,3 post-functionalization, 4

water solubility,5 halogenated derivatives.6 Similarly, there is vast information regarding

their applications: in organic photovoltaic devices,7 as components of novel light active materials,8 as fluorescent tools,9 as sensitizers for dye-sensitized solar cells,10 as sensors for reactive oxygen species,11 and in photodynamic therapy,12 just to mention a few topics. There are well-established fluorophores with a marked diversity of structures that emit at specific wavelengths.13 However, the BODIPYs core structure is one of the few capable to fluoresce over the whole visible and near infrared (NIR) regions of the electromagnetic spectrum, if properly functionalized (Figure 1).2,14


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Figure 1. Panchromatic properties of BODIPY dyes. The possibility to induce a bathochromic shift on the optical properties of these dyes is highly desirable. Many imaginative attempts have been tested to design red-emitting BODIPYs.15 The reason of such search relies on the serious drawbacks of most of the available fluorophores in that spectral region for their optimal practical application.16 As a matter of fact, cyanine dyes are able to provide spectral bands deep in the red edge, even reaching the NIR, but with low fluorescence efficiencies owing to their push-pull and conformationally flexible chromophores.17 On the other hand, oxazine dyes render bright emission but are easily photobleached.18 One way to circumvent such limitations is by shifting the spectral bands of BODIPYs, characterized by their excellent photophysics and robustness,2 to the red edge thanks to the chemical versatility of its dipyrrin core.4 These red-emitting BODIPYs are used as building blocks to prepare polymers that can be used in photovoltaics, solar-cells, photodetectors, etc.19 Such compounds find numerous applications in bio-medicine and related areas. Thus, NIR-emitting BODIPYs have been used as pH probes and in bioimaging,20 in photodynamic therapy,21 and as molecular probes for reactive oxygen species (ROS).22 A well-known approach to red-shift both absorption and emission of BODIPY dyes is to reduce their HOMO-LUMO gap by extending their conjugated system. Thus, the groups of Wu,

23

Rurack,24 Jiao,25 Okujima,26 Ziessel

27

Shinokubo,28 Kubo,29 among others, have

reported a variety of different BODIPY structures featuring extended conjugated systems (Figure 2). Moreover, Wu and Ni have published a review with additional conjugated BODIPY structures.30



OMes

R

OMes

Ph

Ph R

R N

N

N B F F

N B F F R

R

Wu

N X

Ono, Rurack

Br N B F F

Ziessel

N

N B F F

Ph

Ar

N-R

N B F F

OR N

B

N

O O

S R

Ph

Okujima

N

S

S

R

RO

Br N

N B F F R Jiao

Ar S

Page 4 of 63

Ar

R

Kubo

Shinokubo

N N B F F Ar Wu

Figure 2. Representative examples of BODIPYs with extended conjugation. The so-called Keio Fluors 2, are BODIPY dyes with extension of the conjugation including heterocycles, specifically, furan. These feature results in dyes with improved properties, such as color tunability, sharp spectral bands, high extinction coefficients and fluorescence quantum yields. Additionally, they show little dependence of their brightness with solvent polarity. A significant disadvantage is that each derivative must be prepared by a linear synthesis comprising seven steps, leaving little or no room for further modifications of the final products (Scheme 1).31 seven steps Br

O

CHO

O R

O N B F F R Keio Fluors 2 N

Scheme 1. Linear synthesis of Keio Fluors

The synthesis of a single regioisomer 3 was described in 2010, using an alternative methodology (Scheme 2).32


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R

R

4 linear steps N H

R

stepwise Br

N Cl

N B F F Cl

Br N B F F O

N O

cat. Pd(0)

R= Me

N O

N B F F 3

O

Scheme 2. Synthesis of BODIPY 3 After analyzing the synthetic sequence, one realizes that it becomes quite an undertaking to prepare different analogues for each of them would require repeating the whole process to vary the meso-substituent. Moreover, the introduction of additional functional groups on the benzofuran system would need a substituted o-bromophenol. Herein we disclose a fully flexible method that allows the preparation of a novel family of benzofuran-fused BODIPY dyes. Easy modifications in the synthesis permits variations both at the meso-position and the benzofuran substitution pattern since the latter only requires substituted phenols. This method also features the use of an advanced, commercially available BODIPY starting material 4, a complete chemoselective control over three reaction sites, and the preparation of BODIPY dyes with unique architectures and important photophysical and laser properties. In 2016,33 we reported the synthesis of multifunctional BODIPY 5 and demonstrated that it displayed orthogonal reactivity, i.e., the C-S bond was activated under the Liebeskind-Srogl cross-coupling reaction (LSCC)34 conditions, leaving the C-Br bond intact. This chemoselectivity allowed us to introduce a variety of functional groups in a programmed fashion on the periphery of the BODIPY core. Now we decided challenge even further the chemoselectivity of novel BODIPY building block 6 and apply it this time to the preparation of a new family of benzofuran-fused BODIPY dyes (Figure 3).



Previous work:

SMe Suzuki, Stille, Sonogashira

Br

LSCC and SN Ar-like reactions

Br

N

N B F F

Knoevenagel reaction

Suzuki, Stille, Sonogashira

Knoevenagel reaction

5

This work: LSCC reaction

SMe Pd-catalyzed arylations SN Ar-inactive

Br

N Br

N B F F Br

Activated f or SN Ar reactions and f or Pd-catalyzed crosscoupling reactions

6

Br

Pd-catalyzed arylations SN Ar-inactive

Activated f or SN Ar reactions and f or Pd-catalyzed crosscoupling reactions

Figure 3. BODIPY dyes with orthogonal reactivity. This type of benzofuran-fused BODIPYs readily available by this novel approach, display well red-shifted absorption and emission bands. Hereafter, we describe the photophysical and lasing properties of the benzofuran-fused BODIPYs and demonstrate their viability as laser dyes endowed with high laser and fluorescence efficiencies, and high photostability under strong and prolonged pumping. To the best of our knowledge, the laser capabilities of the red-emitting benzo-fused BODIPYs overall are almost hitherto unexploited (just early conference proceedings from SPIE).35


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Results and Discussion Retrosynthetic analysis. The retrosynthetic analysis is shown in Scheme 3. The final products 9 will be formed after a Pd-catalyzed arylation reaction of 8.36 Bis-phenoxycontaining intermediate 8 would be formed after a double SNAr of 7 with substituted phenols under basic conditions, at exclusively at the 3- and 5-positions since only those C-Br bonds are activated towards the addition-elimination process.37 Meso-aryl substituted BODIPY 7 would be prepared from the chemoselective LSCC under neutral conditions leaving intact the four brominated positions.33 This selectivity would allow for the introduction of varied aryl groups at the meso-position, a key step of our synthetic plan. Finally, tetrabrominated intermediate 6 would be produced from commercially available 4. Ar

Pd-catalyzed arylation

R

N O

N B F F

O

Chemoselective LSCC reaction

Ar

Pd-catalyzed arylation

Ar

7

Br

R

N B F F

O

R

9

Br

N

O

8

S N Ar

Br

6

Br

R

1

5

N

N 2 B 3 F F Br

Br

7

S N Ar

SMe

SMe Br

N

N B F F

N Br

4 Commercially available

N B F F Br

Br

6 Facile tetrabromination

Scheme 3. Retrosynthetic analysis to prepare benzofuran-fused BODIPY dyes Synthesis. Tetrabromination of commercially available 8-methylthioBODIPY 4 was carried out according to eq 1. SMe

SMe 5 equiv NBS

N

N B F F 4

Br AcOH, rt, 12 h

N Br

N B F F Br

Br

6, 50%


(1)


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Next, the key step of our synthetic plan followed, i.e., the chemoselective LSCC on 6 in the presence of other reactive sites (Table 1). Table 1. Optimization of the LSCC reaction on 6.a

SMe Br

N Br

N B F F Br

Pd(0) cat, TFP Br +

Cu(I) additive, THF, 55 C, 2 h

N Br

B(OH)2 TFP=

6

Entry

Br

O 3P

N B F F Br

Br

10

Cu source

Pd source

1

Equiv boronic acid 1

CuTCc

Pd2(dba)3

% of conversionb 72

2

3

CuTC

Pd2(dba)3

80

3

3

CuMeSald

Pd2(dba)3

24

4

3

CuO2PPh2e

Pd2(dba)3

65

5

3

CuI

Pd2(dba)3

-f

6

3

CuTC

Pd(PPh3)4g

10

aConditions:

6 (1 equiv), Pd(0) (2.5 mol%), TFP (2.5 mol%), Cu(I) source (equimolar with respect to the boronic acid). bDetermined by HPLC. c Copper(I) thiophene-2-carboxylate. d Copper(I) 3-methylsalicylate. e Copper(I) diphenylphosphinate. f No product was formed. g No TFP was used. The typical Cu(I) sources for the LSCC reaction were tested. All of them, except CuI yielded the desired product (entry 5), however, the best results were observed with CuTC (entry 1). A further increase in the yield was observed when 3 equiv of the boronic acid were used (entry 2). Notably, under these reaction conditions, only BODIPY 10 was produced along with trace amounts of other colored compounds in quantities too small to be characterized.


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This key result allowed the selective functionalization of the meso-position leaving the other brominated positions available to be manipulated at will. Once the best conditions were determined, we set out to react 6 with several arylboronic acids (Table 2) to study the scope of the LSCC reaction. Table 2. LSCC reaction on BODIPY 6.a SMe Br

N Br

N B F F Br

Br + 3 Ar-B(OH)2

Ar

Pd2(dba)3, TFP 3 CuTC, THF, 55 °C

Br

N Br

6

N B F F Br

Br

10-15

Reaction time

% Yieldb

Compound

1

2h

50

10

2

1h

76

11

1h

38

12

40 min

63

13

2h

18

14

1h

83

15

Entry

3 4

Ar-

OHC

MeO

5 6

N

aConditions:

6 (1 equiv), boronic acid (3 equiv), Pd2(dba)3 (2.5 mol%), TFP (2.5%), CuTC (3 equiv), in THF at 55 °C. bIsolated yield. The LSCC took place smoothly in the set of phenols that we studied to give the meso-arylsubstituted products in modest to good yields in relatively short reaction times. Electron-rich boronic acids gave the highest yields (entries 4 and 6). No detrimental effect due to sterics



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was observed when o-tolylboronic acid was employed (entry 2). Once derivatives 10-15 were obtained, the nucleophilic substitution of phenol at the 3-position was explored. The results are given in Table 3. Table 3. Nucleophilic substitution of phenol on derivatives 10-15.a Ar Br

N Br

Ar

OH

N B F F Br

6 equiv Na2CO3

Br + 6

Br

CH3CN, 110 °C

N O

Entry 1

Ar

2 OHC

4

MeO

5 6

Br

16-20

10-15

3

N B F F O

N

Reaction time (h) 6

% Yieldb 80

Compound 16

3

77

17

3

57

18

5

72

19

3

60

20

-

-c

21

aConditions: bIsolated

BODIPYs (1 equiv), phenol (6 equiv), Na2CO3 (6 equiv), sealed tube. yields. cDecomposition of the BODIPY was observed.

Phenol was added to BODIPYs 10-15 under basic conditions in acetonitrile at 110 °C.32 The two-fold substitution reaction took place uneventfully to give 3,5-diphenoxy-subtituted BODIPY dyes in good yields (entries 1-5). However, when trying to add phenol to BODIPY 15, decomposition of this compound was observed. Next, the polyfunctionalized BODIPY so prepared were subjected to the Pd-catalyzed intramolecular arylation (Chart 1).


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Chart 1. Pd-catalyzed arylation of BODIPYs 16-20.a,b Ar Br

Ar

N

N B F F O

O

Pd(OAc)2, PPh3

Br

N

N B F F

O

K2CO3, toluene, 150 °C

16-20

O

22-26 CHO

N

N B F F O 23, 6 h, 66%

N

N B F F O 22, 7 h, 59%a

O

N

N B F F O 24, 5 h, 67%

O

O

OMe

N

N B O F F O 25, 6 h, 48%

N

N B O F F O 26, 6 h, 72%

aConditions:

BODIPY (1 equiv), Pd(OAc)2 (0.05 equiv), PPh3 (0.1 equiv), K2CO3 (3 equiv), in toluene at 150 °C in a sealed tube. bIsolated yield.

In sharp contrast to the reaction conditions that gave rise to isomer 3,38 two-fold arylation reaction of dyes 16-20 was achieved under mild conditions to furnish the cyclized products in yields that ranged from 48% to 72%. The electronic properties of the meso-aryl ring did not seem to have any significant influence in either the reaction time, or the resulting isolated yield. We then decided to study the scope and limitations of the overall process using various substituted phenols (Table 4). Compound 11 was chosen to start the sequence because it has hindered rotation around the Cmeso-aryl bond. This feature increases the probability of



Page 12 of 63

observing a high fluorescent quantum yield (fl) in the final products due to restricted rotation of said bond, thereby inhibiting non-radiative relaxation pathways.39 Table 4. Addition-elimination reaction of substituted phenols on tetrabromoBODIPY 11.a

OH Br

N Br

N B F F Br

Na2CO3

Br +

Br

R

11

Entry 1 2

N

CH3CN, 110 °C

O

OH

F

OH

n-hexyl-O

3

OH

Br

27-31

R

Phenol derivative

N B F F O

R

Reaction time 2h

% Yieldb 79

Compound 27

2h

90

28

1h

90

29

1h

81

30

2h

58

31

2.5 h

-c

32

15 min

-d

33

OH

4 5

OH

I

O 6 7

O

B

OH OH

aConditions:

BODIPY (1 equiv), phenol (6 equiv), Na2CO3 (6 equiv), in MeCN at 110 °C in a sealed tube. bIsolated yields. cThe product decomposed on chromatography (SiO2-gel) purification. dDecomposition was observed. Addition of substituted phenols took place as expected. All the products were obtained, except when 4-hydrophenylpinacol boronate, and 1-hydroxypyrene were used, for decomposition was observed in both cases (entries 6 and 7). Addition of the rest of the


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substituted phenols and naphthol was carried out under mild reaction conditions and short reaction times (1-2 h) to yield the highly colored products in good to excellent yields (entries 1-5). With derivatives 27-31 in hand, we proceeded to study their Pd(0)-catalyzed ring-closure to yield the corresponding benzofuran-fused products. The results are illustrated in Chart 2.

Chart 2. Pd-catalyzed arylation of BODIPYs 27-31.a,b

Br

N O

R

N B F F O

27-31

Br Pd(OAc)2, PPh3 R

K2CO3, toluene, 150 °C


N R

O

N B F F

34-37

O

R


F

F n-hexyl-O

N O

N B F F

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O

N B F F

O

34, 6 h, 75%

O

35, 7 h, 69%

N

N O

N B F F

O-n-hexyl

N

O

O

36, 6 h, 64%

N B F F

O

37, 7 h, 36%

I O

N B F F

I

N

O

38, 30 min, aConditions:

BODIPY (1 equiv), Pd(OAc)2 (0.05 equiv), PPh3 (0.1 equiv), K2CO3 (3 equiv), in toluene at 150 °C in a sealed tube. bIsolated yields.

Satisfyingly, the cyclization reaction took place to produce the final products in moderate to good yields. Iodine-containing derivative 38 was not formed since quick decomposition of the starting material was observed within the first 30 min. Presumably, the more reactive iodide participated in undesired reaction in the presence of Pd. Incorporation of two biomolecules. To demonstrate the applicability of the methodology described herein, two phenolic biomolecules were chosen to be incorporated to the BODIPY core: estrone and N-BOC-L-tyrosine methyl ester. TetrabromoBODIPY 13 was chosen as the starting material since the o-tolyl analogue 11 would give rise to diastereoisomeric final


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products due to its hindered rotation around the meso-sigma bond. To this end, both biomolecules were reacted with 13 under the reaction conditions shown in Tables 3 and 4 (Scheme 4) yielding the expected products in good yields and short reaction times. OMe

O 13 + HO

OMe NHBoc

Na2CO3 CH3CN, 110 °C MeO

NHBoc

Br

N

N B F F O

O

Br

BocHN

OMe

O

O 39, 1 h, 71% MeO

O 13 +

H

Br

Na2CO3

H H

HO

CH3CN, 110 °C

N B F F O

N O

O

H

Br

H

H

H

O

H

H

40, 1 h, 70%

Scheme 4. Reaction of estrone and N-BOC-L-tyrosine methyl ester with BODIPY 13. We then proceeded to carry out the arylation reaction on both 39 and 40 that would produce the final products according to the conditions depicted in Charts 1 and 2. Cyclization of 39 gave the fused derivative 41 in 68% yield after 6 h (eq 2). OMe MeO 39

Pd(OAc)2, PPh3 K2CO3, toluene, 150 °C

O

BocHN

NHBoc N O

N

B F F

O

41, 6 h, 68%


OMe O

(2)


Page 16 of 63

Cyclization of 40 posed an interesting regiochemistry issue since the estrone fragment has two nonequivalent reaction sites (Figure 4). Br

O

H

B F F

O

H H

O

H

O

N

B F F

H

42

H

O

N

H

H

N

H

O 40

B F F

43

Figure 4. The two possible regioisomers that could be produced from the cyclization reaction of 40. Bearing these aspects in mind, the Pd-catalyzed arylation reaction on BODIPY 40 was carried out (eq 3). Even though the overall isolated yield was low (34%), only regioisomer 42 was obtained after 6 h. MeO O

O 40

Pd(OAc)2, PPh3 K2CO3, toluene, 150 °C

H

H H

H

N O

N

B F F

O

H

(3) H

42, 34%, 6 h

Inspection of the NMR data led us to this conclusion. If isomer 43 had been formed, in addition to the characteristic AA´XX´coupling pattern of the 8-(p-MeOphenyl) fragment, and a singlet of the pyrrole moiety, two doublets should appear in the aromatic region due to the cis-hydrogens from the estrone fragment (red protons in Figure 5). On the other hand, if 42 was formed, the two aromatic protons of estrone would be para- to each other (blue protons in Figure 5), and therefore uncoupled. Indeed, the latter is the pattern we observe.


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singlet singlet

O

H

H H

O

H

singlet

H

H H

H

N

N

H

O H

singlet

42

B F F

doublet

O

H

B F F

H doublet NOE

43

Figure 5. Expected 1H NMR signals of isomers 42 and 43. The actual COSY spectrum of 42 is illustrated in Figure 6, showing no cross-peaks between aromatic protons d and e.

Figure 6. Aromatic region of the COSY spectrum of estrone-fused BODIPY 42.

X-ray structure of 25. BODIPY 25 was crystallized by diffusion from petroleum ether/CH2Cl2 (Figure 7). The heterocyclic fragment of 25 is almost planar, displaying a very slight concavity at the center. On the other hand, the B atom has a tetrahedral geometry (the F-B-F angle is 110°, and the N-B-N angle is 104°) and lies off the plane by 10°. The 8-aryl ring is in a 55° angle with respect to the BODIPY plane owing to the steric hindrance between the hydrogens placed at ortho position of the ring and those at the chromophoric positions 1



and 7. The X-ray structure of the tolyl analogue 22, was already reported and displays very similar features.32

Figure 7. X-ray structure of 25 (ORTEP drawing, 50% probability). The corresponding crystallographic date are listed in Table S3.

Photophysical properties The fusion of benzofuran rings to the - positions of the dipyrrin core extends the π-system and, in turn, entails a pronounced bathochromic spectral shift that pushes the spectral band towards the red spectral window (Figure 8 and S1-S3). In contrast, the meso-aryl group has no effect in the spectral band positions. In fact, in the compounds bearing methyl at ortho position of the 8-phenyl, the sterical hindrance places this ring almost orthogonal to the dipyrrin plane (dye 23). But even in absence of such alkylation (dye 22 or 26 for example in Chart 1) the 8-phenyl is also twisted (around 60º) , owing to steric hindrance with the hydrogens at chromophoric positions 1 and 7, and, hence, it is not electronically coupled to the chromophoric core, Such red shift is strengthened by the addition of larger and more conjugated aryls groups to the chromophoric core. For instance, in dye 37, with an aromatic


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framework comprising up to seven aromatic rings, the spectral bands are located well above 600 nm (Figure 8). The electrochemistry measurements reveal that all the dyes have a similar cyclic voltammogram featuring two well-resolved and reversible anodic (around 1.25 V) and cathodic (around -0.75 V) waves (Figure 9 and S4). The extension of the chromophoric framework (dye 37) implies a reduction of both redox potential (with regard to its analog 23, Figure 9), in agreement with the calculated lower energy gap between the frontier molecular orbitals (from 5.80 eV in 23 to 5.73 eV in 37) and the recorded bathochromic shift (Figure 8).

Figure 8. Absorption, normalized fluorescence, and laser (dual emission depending on the dye concentration) spectra of dye 23 and its analogue 37, with additional fused phenyl rings, in ethyl acetate. The spectra of the rest of compounds are included in Figure S1-S3.



Figure 9. Cyclic voltammograms and calculated contour maps and energies of the frontier orbitals for compounds 23 and 37. Additional voltammograms of representative compounds are collected in Figure S4. Despite the number of rings fused to the dipyrrin core, and the ensuing structural stress, the whole chromophore remains planar (for instance, deviations lower than 2º in compound 26, even in the excited state). As a result of this planar and rigid molecular structure, reflected in a low Stokes shift (overall lower than 500 cm-1, Table S1), the aromaticity is high (as testified by Bonds Length Alternation, BLA, parameter around 0.02 in both ground and excited state). These features explain the remarkable high absorption probability (reaching values higher


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than 2·105 M-1 cm-1, Table 5), notable radiative rate constant (kfl > 2·108 s-1, Table 5) and low internal conversion probability (Table 5). Therefore, these conformationally restricted and symmetrical red-emitting dyes display a bright fluorescence response, approaching a 100% in apolar media (Table 5). It should be highlighted that the presence of unconstrained 8-aryl fragments with conformational freedom, efficiently quenches the fluorescence response in simpler and more compact BODIPYs.40 In contrast, in the herein tested dyes, the extension of the -system through the aryls fused to the pyrroles, shifts the electronic density away from the key meso position, avoiding, or at least hampering, the quenching pathway associated to the 8-aryl motion.33 In fact, those dyes sharing the same chromophoric unit (dipyrrin fused with benzofurans), but differing in the meso-substitution, show similar and high fluorescence quantum yields (Table 5) regardless of the conformational mobility of the 8-aryl (unconstrained, twisting angle of the phenyl around 65º in dyes 22 and 26, or constrained, orthogonal ortho-tolyl in 23) or its functionalization (electron donor paramethoxy in 25). The only exception to the rule is 24 with a para-formylated 8-aryl, which shows an unexpected low fluorescence response (Table 5). Such exemption will be rationalized below.

Table 5. Photophysical properties of red-emitting benzofuran-fused BODIPYs in cyclohexane. The whole photophysical data in more solvents are listed in Table S1. λab (nm)

max (104M-1·cm-1)

λfl (nm)

St (cm-1)

ϕ

τ (ns)

kfl (108s-1)

knr (108s-1)

22

548.5

21.5

596.5

345

0.88

4.09

2.15

0.29

23

586.5

21.5

595.5

260

0.88

4.21

2.09

0.29

24

592.5

13.7

612.0

540

0.63

2.47

2.55

1.49

25

583.5

20.0

593.5

290

0.88

4.10

2.14

0.29

26

586.0

15.6

597.5

330

0.84

3.99

2.10

0.40

34

581.5

17.3

590.0

250

0.95

4.02

2.35

0.14



Page 22 of 63

35

592.0

19.0

603.0

310

0.96

4.12

2.33

0.09

36

591.5

23.2

602.0

295

0.89

4.11

2.16

0.27

37

613.0

12.9

625.0

315

0.81

4.31

1.89

0.43

41

586.5

18.0

596.5

285

0.81

3.94

2.07

0.47

42a

596.5

17.9

611.5

410

0.88

4.04

2.18

0.30

a42

was insoluble in cyclohexane, thus, the reported data were recorded in diethylether

The evolution of the fluorescence efficiency with the solvent depends both on the type of functional groups decorating the chromophoric backbone, and on the number of fused rings (Figure 10 and Table S1). Thus, the presence of heteroatoms, like fluorine 34, or alkyl groups (bulky tert-butyl in 36) or a functionalized aliphatic chain (tyrosine biomolecule in 41) in the fused benzofuran, renders highly fluorescent dyes in all the considered solvents. In contrast, the addition of alkoxy chains (35) induces a progressive decrease of both the fluorescence efficiency and the fluorescence lifetime with the solvent polarity (down to 29% and 1.67 ns, respectively, in methanol, Table S1). Such tendency is consistent with the activation of an intramolecular charge transfer (ICT) state in polar media. Thus, the benzofuran itself could act as an electron donor owing to its oxygen heteroatom at the -pyrrolic position. The additional presence of alkoxy groups in the periphery increases such electron donor character, thereby being high enough as to switch on the non-fluorescence ICT. Indeed, in the contour maps depicted in Figure 9, it can be visualized some electron transfer from the benzofuran to the dipyrrin upon excitation (from HOMO to LUMO). Likely, such charge separation is enlarged with fused benzofuran bearing alkoxy moieties, further favoring the non-radiative energy loss through the claimed ICT. Moreover, similar red-emitting dyes have been reported in the literature but with nitrogen instead of oxygen (fusion of indole).41 The higher electron donor ability of the aza group induced a more pronounced spectral red shift but lower fluorescence efficiencies than the herein tested analog 26, likely related to a higher charge


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transfer probability. In this line of reasoning, the presence of electron withdrawing groups at the 8-aryl moiety, albeit moderately weak like the formyl group in dye 24, could reinforce the formation of ICT processes, owing to the induced push-pull character (from the alkoxycontaining benzofuran to the formylated 8-phenyl group), explaining the above-mentioned unexpected quenching of this dye in polar media (Figure 10 and Table 5). To unambiguously back up the ongoing ICT as the key process which rules the fluorescence response in these last dyes (24 and 35), we have measured the photophysical properties of the structurally related analogs 22 (bearing a non-formylated 8-phenyl ring) and 24 (with the said formylated ring) in a battery of solvents with different physicochemical properties (Table S2). Whereas in the former dye 22 the fluorescence quantum yield remains high (always higher than 0.84, Table S2 and Figure S5) regardless of the solvent properties (described by the normalized ET(30) solvent scale42), in the last dye 24 not only the fluorescence quantum yields are lower, but also the values show a marked dependency on the solvent polarity (from 0.63 in cyclohexane down to 0.37 in acetonitrile, Table S2 and Figure S5). Such decrease of the fluorescence efficiency with the solvent polarity is a fingerprint of an ongoing dark ICT, which quenches the emission from the locally excited (LE) state, mainly in polar media where the low-lying ICT is further stabilized. Indeed, the recorded fluorescence quantum yield for dye 24 in a polar/protic solvent (methanol) does not follow the expected trend (Figure S5) and the value is higher (0.44, Table S2). Such exception is likely due to a specific interaction with the electron donor (oxygen atom of the benzofuran) which hampers the population of the photoinduced ICT state.



Figure 10. Evolution of the fluorescence quantum yield of the herein reported novel redemitting BODIPYs with the tested media (from apolar cyclohexane in grey to polar methanol in blue).

On the other hand, compounds 37 and 42, bearing the highest number of fused aryl fragments, show low fluorescence efficiencies in polar media (down to 50% in methanol, Figure 10), albeit the fluorescence lifetimes remain similar (around 3 ns) (Table 5). In these highly extended derivatives, the structural stress to keep the whole chromophore planar should be high, although theoretical calculations predict that the chromophore remains quite planar. However, in the more polar media, where the interactions are stronger, such planarity could be slightly distorted, likely increasing the internal conversion relaxation with the consequent reduction in the fluorescence ability. Alternatively, a further addition of aromatic rings to the chromophoric core could increase the charge separation, enhancing the non-radiative deactivation pathways in polar media.


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Laser Properties In view of the high fluorescence efficiency of these red-emitting dyes, we tested their performance as active media for tunable lasers (see methods in ESI). Owing to the limited solubility of some of the dyes in apolar media, we chose ethyl acetate as the right solvent to measure the laser properties. In addition, this solvent allows assessing the prospects of doping these dyes into solid-state dye lasers (SSDL), as it mimics the chemical structure of methyl methacrylic polymers.43 Hence, the laser characterization and optimization in ethyl acetate could be directly extrapolated to these polymers. Even so, in the most functionalized and largest dyes the solubility was restricted to 0.5 mM (37 and 41) or the required concentration to attain laser emission could not be reached (42).

Table 6. Laser properties of red-emitting benzofuran-fused BODIPYs in ethyl acetate at the optimum dye concentration. The full set of laser data as a function of dye concentration are listed in Table S3. The data corresponding to the commercially available red-emitting BODIPY laser dye (PM650) are included for comparison. Dye

[Dye] Effa λpeak (nm) Edose90% (mM) (%) (GJ/mol) 22 0.75 44 646.5 2.14 23 0.50 48 648.8 3.30 24 0.50 28 636.0 1.07 25 1.00 45 645.2 0.96 26 0.75 44 647.2 1.94 34 1.25 43 642.0 7.39 35 1.25 43 657.6 5.26 36 0.75 43 656.2 4.24 37 0.50 27 685.0 4.46 41 0.50 40 650.0 1.96 PM650 1.00 31 656.5 6.29 aEff:

Laser efficiency or ratio of output/input energy; λpeak: Laser peak wavelength; Edose90% : Molar energy dose needed to reduce LIF to a 90% of its initial value (see methods for a detail description).



The laser properties correlate, grosso modo, with the photophysical signatures (Table 5 and S1). At high concentrations, all the dyes (with the aforementioned exception of 42 owing to solubility reasons) display a laser emission line far away from the absorption and fluorescence band (around 70 and 50 nm, respectively), much stronger than what is usually recorded for BODIPY dyes (around 40 and 20 nm, respectively).44 In particular, dye 37 presents the redder laser band, which is centered at 685 nm thanks to its higher number of aromatic rings fused to the chromophoric core (Figure 8). In contrast, at low concentrations or low pump energies, the laser emission band appears in the expected position for BODIPYs (Figure 8), leading, in some cases, to bichromatic emission (Figure 11 and Table S3). Such dual laser emission has been previously ascribed to the formation of excited state aggregates (excimers or super-exciplexes) under strong laser pumping conditions of high optical density active media,45 hence it is absent in the photophysical measurements. In this sense, the laser band recorded for these dyes at high concentrations in ethyl acetate corresponds to an aggregated form of the dyes, whereas the blue-shifted laser band at low concentrations corresponds to the dye in monomeric form (Figure 11). The presence of this kind of aggregates also enables widening the tuning range.45b


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Figure 11. Normalized laser spectra (left) and output energy (right) as a function of pump energy for dye 25 0.38 mM in ethyl acetate. With regard to the laser efficiencies, those dyes which showed high fluorescence efficiency regardless of the surrounding media (22, 23, 25, 26, 34, 36 and 41) display high laser efficiencies (surpassing the 40% at the optimal concentration). On the other hand, those dyes which rendered the lowest fluorescence efficiencies (24 and 37) show accordingly the worst laser efficiency (lower than 30%). The only exception to such good correlation is dye 35, which underwent an ICT process. Indeed, in spite of its low fluorescence response, the recorded laser efficiency for 35 places this compound amongst the best ones in this study. Such apparent mismatch can be rationalized considering the shorter excited-state lifetime of such dye, which favors the stimulated radiative deactivation and compensates for the low spontaneous emission probability. An analogous behavior was reported previously for LDS722, a hemicyanine dye with a quantum yield as low as 14% but a 43% laser efficiency owing to a lifetime of around 500 ps.46 Most of the dyes show a good tolerance to a prolonged and intense laser pumping, with the exception of the dyes bearing methoxy (25 and 41) or formyl (24) functional groups at para position of the 8-phenyl ring. Indeed, more than 3



GJ/mol are required to decrease the laser output energy to a 90% of its initial value, outstanding the fluorinated dye 34, which is able to tolerate up to 7.4 GJ/mol before the same energy loss is recorded (Table 6). These results are consistent with a previously reported strategy based on the fluorination of organic dyes, which enabled achieving long lasting active media even under drastic pumping regime.47 To put these results into perspective, we compared the laser performance of these red emitting laser dyes with that of the commercially available BODIPY PM650, consisting of a methylated dipyrrin core with a cyano group at the meso position, that emits in the same spectral region.43 This dye is very photostable (tolerance up to 6.3 GJ/mol) owing to the electron withdrawing character of the said cyano group, which reduces the reactivity against the oxidizing ambient oxygen, involved in the photodegradation mechanism.48 At the same time, such functionalization enables the population of ICT states. Such non-radiative deactivation channel shortens the lifetime, supporting the recorded moderately high laser efficiencies (30%, Table 6) in spite of its reduced fluorescence efficiency. The photostability of most of the herein tested dyes are lower than that of PM650, albeit some of them to reach close values, outstanding dye 34 whose photostability even surpasses that of the reference PM650. On the other hand, the recorded laser efficiencies of most of the herein tested dyes (mainly, 22, 23, 25, 26, 34, 36 and 41) improve that displayed by PM650. Therefore, the herein reported benzofuran-fused BODIPYs are suitable candidates to develop efficient redemitting lasers with a reasonable photostability.

Conclusions We have described a novel synthetic methodology to prepare benzofuran-fused BODIPY dyes in four steps starting from commercially available 8-methylthioBODIPY 4. Careful


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selection of the reaction conditions permitted the chemoselective functionalization of the meso-position of multiply functionalized BODIPY 6. SNAr-like reaction of phenolates exclusively at the 3- and 5-positions allow the positioning of such moiety for the final intramolecular Pd(0)-catalyzed arylation at the 2- and 6-positions of the BODIPY nucleus. The herein reported synthetic avenue allows not only an easy access to benzofuran-fused BODIPYs with different substitution pattern, but also enables to incorporate relevant biomolecules to the BODIPYs core. Once these biomolecules are endowed with new fluorescent properties, they may find very interesting biology-related applications such as sensors, cell-imaging, protein-labeling, and so on. The extended aromatic framework of these conformationally restricted BODIPYs renders strong absorption, fluorescence and laser bands shifted to the red edge of the visible. Indeed, the fluorescence and laser efficiencies reach almost the 100% and are above 40%, respectively, in the best cases. It is worthy to note that the laser emission is rather intriguing displaying a deep shift towards the red edge owing to the promotion of excited state aggregates at high concentration and under intense laser pumping. Therefore, these -extended BODIPYs show nice behavior as red laser dyes in terms of efficiency and photostability, since up to 7.3 GJ per mol of dye are required to induce a decrease of the output laser emission of just a 10%, overcoming the limitations of most of the commercially available dyes (such as cyanines or oxazines) in such spectral region. This method is amenable to grafting other heterocycles such as indoles and benzothiophenes by adding either anilines or thiophenols. We are currently exploring these possibilities as well as the cell-imaging properties of both 41 and 42. The results will be reported in due course.

Experimental



Photophysical properties: Spectroscopic properties were registered in diluted solutions (around 2×10–6 M), prepared by adding the corresponding solvent (spectroscopic grade) to the residue from the adequate amount of a concentrated stock solution in acetone, after vacuum evaporation of this solvent. UV-Vis absorption, and fluorescence spectra and decay curves were recorded on a Varian model CARY 4E spectrophotometer and an Edinburgh Instruments spectrofluorimeter (model FLSP 920), respectively. Fluorescence quantum yields () were obtained using as reference commercial cresyl violet (r = 0.54 in methanol). The values were corrected by the refractive index of the solvent. Radiative decay curves were registered with the time correlated single-photon counting technique using a multichannel plate detector with picosecond time-resolution. Fluorescence emission was monitored at the maximum emission wavelength after excitation by means of a wavelength-tunable Fianium Supercontinuum laser. The fluorescence lifetime () was obtained after the deconvolution of the instrumental response signal from the recorded decay curves by means of an iterative method. The goodness of the exponential fit was controlled by statistical parameters (chisquare and the analysis of the residuals). The radiative (kfl) and non-radiative (knr) rate constants were calculated from the fluorescence quantum yield and lifetime; kfl = / and knr = (1-)/. Quantum mechanical calculations: Ground state geometries were optimized at the Density Functional Theory (DFT) using range-separated hybrid wB97XD method, whereas the first singlet excite state was optimized by the Time Dependent (TD) method and the same functional. In both cases the triple valence basis set with two polarization functions (6311g**) was used. The geometries were considered as energy minimum when the corresponding frequency analysis did not give any negative value. The solvent effect (ethyl


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acetate) was considered in the conducted theoretical simulations by means of the Polarizable Continuum Model (PCM). All the calculations were performed using the Gaussian 16 software as implemented in the computational cluster “arina” of the UPV/EHU. Electrochemistry: Cyclic voltammograms (Metrohm Autolab) were done using a threeelectrode set up with a platinum layer (surface 8 mm x 7.5 mm) working electrode, platinum wire as counter electrode and Ag/AgCl as reference electrode. A 0.1 M solution of tetrabutylammonium hexafluorophosphate (TBAPF6) in dry acetonitrile was used as the electrolyte solvent in which the compounds were dissolved to achieve a concentration of around 1 mM. All redox potentials were reported vs ferrocene as internal standard. The solutions were purged with argon and all the measurements were performed under an inert atmosphere. Laser measurements set-up: Liquid solutions of dyes in ethyl acetate were contained in 1 cm optical-path rectangular quartz cells carefully sealed to avoid solvent evaporation during experiments. The liquid solutions were transversely pumped with 20 ns full width at half maximum (FWHM) pulses from a frequency-doubled (532nm) Q-switched Nd:YAG laser (Lotis TII SL-2132) at a repetition rate of 1 Hz. The exciting pulses were line-focused onto the cell using a combination of positive and negative cylindrical lenses (f=15cm and f=15cm, respectively) perpendicularly arranged. The plane parallel oscillation cavity (2 cm length) consisted of a 90% reflectivity aluminum mirror acting as back reflector, and with the lateral face of the cell acting as output coupler (4% reflectivity). The pump and output energies were detected by a calibrated Laser Energy Meter (QE 12LP-S-MB-DO, Gentec). The output laser emission was directed towards a fiber bundle and detected with a spectrograph/monochromator (Spectrapro-300i Acton Research) equipped with a thermoelectrically cooled CCD detector (SpectruMM:GS 128B). A shortwave Cut-off filter



Page 32 of 63

(OptoSigma, cut-off at 540 nm) was placed before the fibre bundle to avoid any scattered pump light entering the spectrograph. Neutral density filters were used to avoid CCD detector saturation. The photostability of the dyes in ethyl acetate solution was evaluated by using a pumping energy and geometry exactly equal to that of the laser experiments. We used spectroscopic quartz cuvettes with 1 cm optical paths and depths L = 0.1 cm to allow for the minimum solution volume (VS = 60 μL) to be excited. The lateral facets were grounded, whereupon no laser oscillation was obtained. Nevertheless, information about photostabilities can be obtained by monitoring the decrease in laser-induced fluorescence (LIF) intensity. In order to facilitate comparisons independently of the experimental conditions and sample, the photostability figure of merit was defined as the accumulated pump energy absorbed by the system (Edose), per mole of dye, before the output energy falls to a 90% its initial value. In terms of experimental parameters, this energy dose, in units of GJ mol-1, can be expressed as:





E pump (GJ )  1  10 CL · 90% E dose (GJ ·mol 1 )



f

#pulses

CVS

(1)

where Epump is the energy per pulse in GJules, C is the molar concentration, ε is the molar absorption coefficient in units of M-1 cm-1, L is the depth of the cuvette expressed in cm, VS is the solution volume, in liters, within the cuvette, and f is the ratio between the LIF intensity after #pulses and the LIF intensity in the first pulse. It can be shown that Σf accounts for . the reduction in pump absorption due to species photo-degradation. To speed up the experiment the pump repetition rate was increased up to 15Hz. The fluorescence emission was monitored perpendicular to the exciting beam, collected by an optical fiber, and acquired using the previously described spectrograph/monochromator system.


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X-ray Crystal Structure determination: Intensity data were collected on an Agilent Technologies Super-Nova diffractometer, which was equipped with monochromated Cu kα radiation (λ= 1.54184 Å) and Atlas CCD detector. Measurement was carried out at 99.99(10) K with the help of an Oxford Cryostream 700 PLUS temperature device. Data frames were processed (united cell determination, analytical absorption correction with face indexing, intensity data integration and correction for Lorentz and polarization effects) using the Crysalis software package. The structure was solved using Olex2 and refined by full-matrix least-squares with SHELXL-97. Final geometrical calculations were carried out with Mercury and PLATON as integrated in WinGX. Crystallographic data (excluding structure factors) for the structure(s) reported in this paper have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication no. CCDC-1877155. Copies of the data can be obtained free of charge from www.ccdc.cam.ac.uk/conts/retrieving.html.

Synthesis and characterization:

1H

and

13C

NMR spectra were recorded in

deuteriochloroform (CDCl3), with either tetramethylsilane (TMS) (0.00 ppm 1H, 0.00 ppm 13C),

chloroform (7.26 ppm 1H, 77.00 ppm 13C). Data are reported in the following order:

chemical shift in ppm, multiplicities (br (broadened), s (singlet), d (doublet), t (triplet), q (quartet), m (multiplet), exch (exchangeable), app (apparent)), coupling constants, J (Hz), and integration. Infrared spectra were recorded on a FTIR spectrophotometer. Peaks are reported (cm-1) with the following relative intensities: s (strong, 67–100 %), m (medium, 40– 67%), and w (weak, 20–40%). Melting points are not corrected. TLC was conducted in Silica gel on TLC Al foils. Detection was done by UV light (254 or 365 nm). HRMS samples were ionized by ESI+ and recorded via the TOF method.



Materials. Starting 8-methylthioBODIPY, CuTC, tri(2-furyl)phosphine, and boronic acids are commercially available. Solvents were dried and distilled before use. General Procedure for the L−S Cross-Coupling reaction (GP1). A Schlenk tube equipped with a stir bar was charged with 6 (1.0 equiv), the corresponding boronic acid (3.0 equiv), and dry THF (0.03 M). The mixture was sparged with N2 for 3 min, whereupon Pd2(dba)3 (2.5 mol %), trifurylphosphine (7.5%), and CuTC (3.0 equiv) were added under N2. The Schlenk tube was then immersed in a preheated oil bath at 55 °C. The oil bath was removed after the starting material 6 BODIPY was consumed (TLC, AcOEt/hexanes). After the mixture reached rt, the solvent was removed and the crude material was adsorbed in SiO2 gel, dried under reduced pressure, and purified by flash chromatography on SiO2 gel using AcOEt/hexanes as eluent. General Procedure for the nucleophilic substitution with phenols and phenol derivatives (GP2). A sealed tube with a stir bar was charged with the corresponding BODIPYs (10-15) (1.0 equiv), phenol or phenol derivatives (4 or 6 equiv), Na2CO3 (5 or 6 equiv) and acetonitrile (0.02M), then the mixture was sparged with N2 during 5 minutes. The tube was sealed, and the solution was stirred at 110 °C until competition (TLC monitoring, AcOEt/hexanes, THF/hexane or acetone/hexane as indicate). The oil bath was removed after the starting BODIPY was consumed. After the mixture reached rt, the solvent was removed under reduced pressure, and the crude material was adsorbed in SiO2 gel, dried under vacuum and purified by flash chromatography on SiO2 gel using THF/hexanes, acetone/hexanes, CHCl3/hexanes or AcOEt/hexanes as indicated. General Procedure for the cyclization reaction (GP3). A sealed tube with a stir bar was charged with the corresponding BODIPY (16-21, 27-33) (1.0 equiv), Pd(OAc)2 (0.05 equiv), PPh3 (0.1 equiv), K2CO3 (3 equiv) and toluene, then the mixture was sparged with N2


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during 5 min. The tube was sealed, and the solution was stirred at 150 °C until completion (TLC monitoring, AcOEt/hexanes, THF/hexane or CHCl3/hexane as indicate). The oil bath was removed after the starting BODIPY was consumed. After the mixture reached rt, the solvent was removed under reduced pressure, and the crude material was adsorbed in SiO2 gel, dried under vacuum and purified by flash chromatography on SiO2 gel using acetone/hexanes or CHCl3/hexanes as indicated. Synthesis of 6. A round-bottom flask under N2 was charged

S

with 4 (30 mg, 0.126 mmol, 1 equiv), N-bromosuccinimide Br Br

N N B F F Br 6

Br

(112.1 mg, 0.63 mmol, 5.0 equiv) and acetic acid (4.2 mL). The reaction mixture was stirred at room temperature

overnight whereupon water (30 mL) was added and the pH was adjusted using saturated Na2CO3 to pH 7. The product was extracted with ethyl acetate, washed with brine (5 x 20 mL), dried with anhyd. MgSO4, and filtered. The solvent was removed under reduced pressure, and the crude product was adsorbed in SiO2 gel, dried under vacuum, and purified by flash chromatography using 10% EtOAc/hexanes. The desired product (20 mg, 0.036 mmol, 70%) was obtained as a dark red solid. TLC (15% EtOAc/hexanes, Rf = 0.25); mp 212-214°C; IR (KBr, cm-1): 2669 (w), 1516 (s), 1441 (m), 1364 (s), 1335 (s), 1303 (m), 1237 (s), 1161 (s), 1097 (s), 979 (m), 966 (m), 916 (s), 819 (w), 808 (w), 744 (w), 632 (w), 587 (w), 502 (w); 1H NMR (500 MHz, CDCl3) δ 7.44 (s, 2H), 2.83 (s, 3H). 13C {1H} (126 MHz, CDCl3): δ 147.7, 134.9, 133.5, 128.7, 111.8, 21.5. HRMS (ESI+) m/z calcd for C10H5BBr4F2N2SK [M+K]+ 592.6560. Found 592.6547. Synthesis of 10.49 According to GP1. 6 (25 mg, 0.045 mmol), p-tolylboronic acid (18.4 mg, 0.135 mmol), Pd2(dba)3 (1.0 mg, 1.1 × 10−3 mmol), TFP (0.79 mg, 3.4 × 10−3 mmol), and CuTC Br Br

N N B F F Br 10

Br ACS Paragon Plus Environment


(25.8 mg, 0.135 mmol). After 2 h the crude was purified using 0.2% AcOEt/hexanes. The desired product (13 mg, 0.022 mmol, 48%) was obtained as dark red solid. TLC (20% THF/hexanes, Rf = 0.79); mp >260 °C decompose.; 1H NMR (500 MHz, CDCl3): δ 7.38 (d, J = 8.1 Hz, 2H), 7.35 (d, J = 8.2 Hz, 2H), 6.93 (s, 2H), 2.47 (s, 3H). HRMS (ESI+) m/z calcd for C17H10BBr4F2N2 [M+H]+ 598.7596. Found 598.7619.

Synthesis of 11. According to GP1. 6 (20 mg, 0.036 mmol), otolylboronic acid (14.7 mg, 0.108 mmol), Pd2(dba)3 (0.82 mg, Br Br

N N B F F Br 11

Br

9.0 × 10−4 mmol), TFP (0.63 mg, 2.7 × 10−3 mmol), and CuTC (20.7 mg, 0.108 mmol). After 2 h the crude material was purified using 3% AcOEt/hexanes. The desired product (16.5

mg, 0.027 mmol, 76% yield) was obtained as dark red crystals. TLC (20% AcOEt/hexanes, Rf = 0.57); mp >260°C dec.; IR (KBr, cm−1): 3679 (w), 2921 (w), 2661 (w), 1554 (s), 1539 (s), 1488 (m), 1452 (w), 1354 (s), 1312 (s), 1247 (s), 1225 (s), 1179 (s), 1141 (s), 1083 (s), 1014 (m), 999 (m), 905 (m), 839 (m), 819 (m), 737 (s), 701 (m), 651 (w), 597 (w), 543 (w), 488 (w); 1H NMR (500 MHz, CDCl3): δ 7.45 (t, J = 7.1 Hz, 2H), 7.35 - 7.28 (m, 2H), 7.21 (d, J = 7.4 Hz, 2H), 6.68 (s, 2H), 2.23 (s, 3H). 13C {1H} (126 MHz, CDCl3) δ 142.5, 136.6, 135.7, 135.4, 131.0, 131.0, 130.9, 130.6, 129.9, 125.9, 112.3, 20.2. HRMS (ESI+) m/z calcd for C16H10BBr4F2N2 [M+H]+ 598.7596. Found 598.7620.


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O

Synthesis of 12. According to GP1. 6 (10 mg, 0.02 mmol), p-

H

formylphenyl boronic acid (5.4 mg, 0.04 mmol), Pd2(dba)3 (0.4 mg, 5.0 × 10−4 mmol), TFP (0.3 mg, 1.4 × 10−3 mmol), and Br Br

N N B F F Br 12

Br

CuTC (10.3 mg, 0.05 mmol). After 1 h the crude material was purified using 5% AcOEt/hexanes. The desired product (4.2 mg, 0.007 mmol, 38% yield) was obtained as green crystals.

TLC (15% AcOEt/hexanes, Rf = 0.46); mp 271-272 °C; IR (KBr, cm−1): 3679 (w), 3120 (w), 1701 (s), 1573 (s), 1551 (s), 1447 (w), 1357 (s), 1314 (m), 1287 (w), 1238 (s), 1207 (w), 1179 (w), 1097 (s), 1018 (w), 995 (m), 833 (m), 753 (m), 705 (m), 652 (w), 486 (w); 1H NMR (500 MHz, CDCl3): δ 10.15 (s, 1H), 8.07 (d, J = 8.0 Hz, 2H), 7.67 (d, J = 8.0 Hz, 2H) 6.85 (s, 3H). 13C{1H} (126 MHz, CDCl3): δ 191.0, 140.5, 138.2, 137.3, 136.6, 134.7, 131.3, 131.0, 130.0, 112.8. HRMS (ESI+) m/z calcd for C16H7BBr4F2N2ONa [M+Na]+ 634.7208. Found 634.7212.

Synthesis of 13.50 According to GP1. 6 (20 mg, 0.036 mmol),

OMe

p-methoxyphenyl boronic acid (16.5 mg, 0.108 mmol), Pd2(dba)3 (0.83 mg, 9.0 × 10−4 mmol), TFP (0.63 mg, 2.7 × 10−3 Br Br

N N B F F Br 13

Br

mmol), and CuTC (20.7 mg, 0.11 mmol). After 3 h the crude was purified using 15% AcOEt/hexanes. The desired product (14 mg, 0.023 mmol, 63% yield) was obtained as dark red solid.

TLC (20% AcOEt/hexanes, Rf = 0.5); mp 238-239 °C; 1H NMR (500 MHz, CDCl3): δ 7.46 (d, J = 8.7 Hz, 2H), 7.06 (d, J = 8.7 Hz, 2H), 6.95 (s, 2H), 3.92 (s, 3H). HRMS (ESI+) m/z calcd for C16H9BBr4F2N2ONa [M+Na]+ 636.7366. Found 636.7364.



Synthesis of 14.50 According to GP1. 6 (50 mg, 0.090 mmol), phenylboronic acid (40.0 mg, 0.072 mmol), Pd2(dba)3 (1.7 mg, Br Br

N N B F F Br 14

Br

1.8 × 10−3 mmol), TFP (1.3 mg, 5.4 × 10−3 mmol), and CuTC (41.3 mg, 0.260 mmol). After 2 h the crude was purified using 1% AcOEt/hexane. The desired product (9.5 mg, 0.016 mmol,

18%) was obtained as purple solid. TLC (10% AcOEt/hexanes, Rf = 0.48); mp >200 °C dec.; 1H

NMR (500 MHz, CDCl3): δ 7.63 (t, J = 7.4 Hz, 1H), 7.55 (t, J = 7.6 Hz, 2H), 7.48 (d, J =

7.2 Hz, 2H), 6.90 (s, 1H). HRMS (ESI+) m/z calcd for C15H7BBr4F2N2Na [M+Na]+ 606.7259. Found 606.7278.

Synthesis of 15. According to GP1. 6 (50 mg, 0.09 mmol), 4N

(dimethylamino)phenyl boronic acid (44.7 mg, 0.27 mmol), Pd2(dba)3 (2.07 mg, 2.3 × 10−3 mmol), TFP (1.6 mg, 6.8 × 10−3

Br Br

N N B F F Br 15

Br

mmol), and CuTC (51.7 mg, 0.27 mmol). After 50 min the crude material was purified using 30% AcOEt/hexanes. The desired product (30 mg, 0.048 mmol, 53% yield) was obtained as dark

blue solid. TLC (20% AcOEt/hexanes, Rf = 0.2); mp 221-223 °C; IR (KBr, cm−1): 2918 (w), 1602 (s), 1542 (w), 1512 (m), 1493 (m), 1431 (w), 1403 (w), 1361 (s), 1328 (m), 1283 (m), 1254 (m), 1195 (m), 1106 (m), 1004 (w), 984 (m), 976 (m), 826 (w), 751 (w), 647 (w), 537 (w); 1H NMR (500 MHz, CDCl3): δ 7.45 (d, J = 8.8 Hz, 2H), 7.01 (s, 2H), 6.79 (d, J = 8.8 Hz, 2H), 3.13 (s, 3H).

13C{1H}

(126 MHz, CDCl3): δ 153.3, 144.4, 134.3, 133.4, 131.6,


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131.0, 119.9, 112.0, 110.8, 40.3. HRMS (ESI+) m/z calcd for C17H13BBr4F2N3 [M+H]+ 627.7862. Found 627.7854.

Synthesis of 16. According to GP2. 10 (46.0 mg, 0.08 mmol), phenol (36.2 mg, 0.39 mmol), Na2CO3 (40.8 Br

Br

N N B O F F O 16

mg, 0.39 mmol) and acetonitrile (4 mL). The reaction mixture was stirred at 110 °C for 6 h. The crude was purified using 1% AcOEt/hexanes. The desired

product (19.4 mg, 0.032 mmol, 80% yield) was obtained as red crystals. TLC (10% AcOEt/hexanes, Rf = 0.26); mp 197-199 °C; IR (KBr, cm−1): 3679 (w), 2971 (w), 1571 (m), 1553 (m), 1546 (m), 1501 (m), 1485 (m), 1448 (s), 1333 (w), 1253 (s), 1204 (w), 1181 (m), 1128 (s), 1038 (s), 1003 (w), 988 (w), 840 (m), 711 (w); 1H NMR (500 MHz, CDCl3): δ 7.44 (d, J = 8.0 Hz, 2H), 7.38 - 7.30 (m, 6H), 7.16 - 7.09 (m, 6H), 6.94 (s, 2H), 2.48 (s, 2H). 13C{1H}

(126 MHz, CDCl3): δ 157.9, 155.8, 142.6, 141.6, 132.1, 130.5, 129.8, 129.6, 129.5,

127.7, 124.6, 117.9, 96.1, 21.6. HRMS (ESI+) m/z calcd for C28H19BBr2F2N2O2Na [M+Na]+ 646.9753. Found 646.9743.

Synthesis of 17. According to GP2. 11 (43.0 mg, 0.07 mmol), phenol (33.8 mg, 0.36 mmol), Na2CO3 (38.1 mg, Br

N N B O F F O 17

Br

0.36 mmol) and acetonitrile (4 mL). The reaction mixture was stirred at 110 °C for 3 h. The crude was purified using 1% AcOEt/hexanes. The desired product

(34.6 mg, 0.055 mmol, 77% yield) was obtained as red crystals. TLC (10% AcOEt/hexanes, Rf = 0.30); mp 202-203 °C; IR (KBr, cm−1): 3672 (w), 2972 (w), 2917 (w), 1563 (m), 1485



(m), 1450 (s), 1352 (w), 1337 (w), 1251 (s), 1197 (m), 1182 (m), 1118 (s), 1034 (s), 1003 (w), 912 (w), 839 (m), 741 (m), 706 (w), 685 (w); 1H NMR (500 MHz, CDCl3): δ 7.46 - 7.41 (m, 1H), 7.37 -7.27 (m, 7H), 7.17 - 7.10 (m, 6H), 6.69 (s, 2H), 2.31 (s, 3H). 13C{1H} (126 MHz, CDCl3): δ 158.1, 155.7, 141.7, 136.9, 131.5, 131.4, 130.8, 130.3, 130.1, 129.8, 128.1, 125.7, 124.7, 118.0, 96.2, 20.2. HRMS (ESI+) m/z calcd for C28H20BBr2F2N2O2 [M]+ 624.9933. Found 624.9934.

O

Synthesis of 18. According to GP2. 12 (20.0 mg, 0.03

H

mmol), phenol (18.5 mg, 0.20 mmol), Na2CO3 (20.8 mg, 0.20 mmol) and acetonitrile (2 mL). The reaction Br

N N B O F F O 18

Br

mixture was stirred at 110 °C for 3 h. The crude material was purified using 10% AcOEt/hexanes. The desired product (12.0 mg, 0.019 mmol, 57% yield) was

obtained as red crystals. TLC (20% AcOEt/hexanes, Rf = 0.30); mp 112-113 °C; IR (KBr, cm−1): 3694 (w), 2973 (w), 1704 (m), 1574 (m), 1556 (m), 1500 (m), 1450 (s), 1350 (w), 1253 (s), 1201 (m), 1182 (m), 1123 (s), 1037 (s), 1003 (m), 833 (m), 757 (w), 686 (w); 1H NMR (500 MHz, CDCl3): δ 10.15 (s, 1H), 8.07 (d, J = 8.2 Hz, 2H), 7.72 (d, J = 8.1 Hz, 2H) 7.37 - 7.30 (m, 4H), 7.16 (t, J = 7.4 Hz, 2H), 7.13 - 7.10 (m, 4H), 6.86 (s, 2H). 13C{1H} (126 MHz, CDCl3): δ 191.3, 158.6, 155.6, 139.8, 138.0, 137.8, 131.8, 131.1, 129.9, 129.9, 127.4, 124.9, 118.0, 96.7. HRMS (ESI+) m/z calcd for C28H18BBr2F2N2O3 [M+H]+ 638.9726. Found 638.9730. OMe

Synthesis of 19. According to GP2. 13 (34.5 mg, 0.06 mmol), phenol (26.4 mg, 0.29 mmol), Na2CO3 (29.8 Br

N N B O F F O 19

Br ACS Paragon Plus Environment

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mg, 0.28 mmol) and acetonitrile (3 mL). The reaction mixture was stirred at 110 °C for 5.5 h. The crude material was purified using 2% AcOEt/hexanes. The desired product (25.9 mg, 0.040 mmol, 72% yield) was obtained as orange crystals. TLC (10% AcOEt/hexanes, Rf = 0.08); mp 237-238 °C; IR (KBr, cm−1): 3694 (w), 2972 (w), 2917 (w), 2845 (w), 1605 (w), 1575 (m), 1551 (s), 1500 (m), 1485 (m), 1452 (s), 1444 (s), 1351 (w), 1333 (w), 1297 (w), 1256 (s), 1182 (s), 1130 (s), 1108 (s), 1039 (s), 1020 (m), 838 (s), 716 (m), 684 (w), 606 (w), 575 (w); 1H NMR (500 MHz, CDCl3): δ 7.50 (d, J = 8.7 Hz, 2H), 7.35 - 7.30 (m, 4H), 7.17 - 7.05 (m, 8H), 6.96 (s, 2H), 3.92 (s, 3H). 13C{1H} (126 MHz, CDCl3): δ 162.2, 157.7, 155.9, 142.4, 132.3, 132.0, 129.8, 127.6, 124.7, 124.6, 117.9, 114.5, 96.0, 55.73. HRMS (ESI+) m/z calcd for C28H20BBr2F2N2O3 [M+H]+ 640.9883. Found 640.9867.

Synthesis of 20. According to GP2. 14 (31 mg, 0.05 mmol), phenol (25 mg, 0.27 mmol), Na2CO3 (28.1 Br

N N B O F F O 20

Br

mg,0.27 mmol) and acetonitrile (2.5 mL). The reaction mixture was stirred at 110 °C for 3 h. The crude material was purified using 2% AcOEt/hexanes. The desired

product (38.4 mg, 0.062 mmol, 60% yield) was obtained as red crystals. TLC (10% AcOEt/hexanes, Rf = 0.30); mp 213-214 °C; IR (KBr, cm−1): 3368 (w), 2972 (w), 1578 (w), 1551 (s), 1502 (m), 1485 (m), 1451 (s), 1440 (s), 1333 (w), 1289 (w), 1253 (s), 1206 (w), 1182 (m), 1123 (s), 1038 (s), 1003 (w), 988 (w), 840 (m), 731 (w), 718 (w), 605 (w); 1H NMR (500 MHz, CDCl3): δ 7.62 - 7.58 (m, 1H), 7.35 - 7.31 (m, 4H), 7.16 - 7.09 (m, 6H), 6.92 (s, 2H). 13C{1H} (126 MHz, CDCl3): δ 158.1, 155.8, 142.2, 132.3, 132.1, 130.9, 130.5, 129.8, 128.9, 127.7, 124.7, 117.9, 96.2. HRMS (ESI+) m/z calcd for C27H18BBr2F2N2O2 [M+H]+ 610.9777. Found 610.9767.



Synthesis of 22. According to GP3. 16 (30.0 mg, 0.05 mmol), Pd(OAc)2 (0.54 mg, 2.4 x 10-3 mmol, 0.05 equiv), PPh3 (1.3 mg, 4.8 x 10-3 mmol, 0.1 equiv),

O

N N B F F 22

K2CO3 (19.9 mg, 0.14 mmol, 3 equiv) and toluene (4 O

mL). The reaction mixture was stirred at 150 °C for 7

h. The crude material was purified using 80% CHCl3/hexanes. The desired product (13.0 mg, 0.04 mmol, 59% yield) was obtained as a golden solid. TLC (20% THF/hexanes, Rf = 0.3); mp 263-265 °C; IR (KBr, cm−1): 2921 (w), 1628 (w), 1577 (s), 1478 (m), 1449 (s), 1442 (s), 1408 (s), 1367 (s), 1348 (s), 1323 (s), 1291 (m), 1277 (m), 1186 (w), 1159 (m), 1143 (s), 1113 (s), 1012 (w), 987 (s), 926 (w), 818 (m), 808 (m), 760 (w), 743 (m), 714 (w), 696 (w), 555 (m), 467 (w); 1H NMR (500 MHz, CDCl3): δ 7.60 - 7.50 (m, 6H), 7.38 (d, J = 7.7 Hz, 2H), 7.33 (t, J = 7.3 Hz, 2H), 7.29 - 7.24 (m, 3H), 6.87 (s, 2H), 2.51 (s, 3H). 13C{1H} (126 MHz, CDCl3): δ 167.4, 161.0, 145.9, 140.8, 134.6, 130.9, 130.5, 129.3, 126.6, 124.7, 121.6, 121.6, 118.7, 118.1, 113.2, 21.6. HRMS (ESI+) m/z calcd for C28H18BF2N2O2 [M+H]+ 463.1429. Found 463.1419.

Synthesis of 23. According to GP3. 17 (30.0 mg, 0.05 mmol), Pd(OAc)2 (0.54 mg, 2.4 x 10-3 mmol, 0.05

O

N N B F F 23

equiv), PPh3 (1.3 mg, 4.8 x 10-3 mmol, 0.1 equiv), K2CO3 O

(19.9, 0.14 mmol, 3 equiv) and toluene (4 mL). The reaction mixture was stirred at 150 °C for 6 h. The crude

was purified using 60% CHCl3/hexanes. The desired product (14.7 mg, 0.04 mmol, 66% yield) was obtained as a golden solid. TLC (60% CHCl3/hexanes, Rf = 0.3); mp >300 °C


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dec.; IR (KBr, cm−1): 3352 (w), 3066 (w), 2972 (w), 1627 (m), 1578 (s), 1477 (m), 1448 (s), 1441 (s), 1344 (s), 1319 (s), 1292 (s), 1185 (w), 1158 (s), 1140 (s), 1107 (s), 1012 (m), 985 (s), 818 (s), 762 (m), 745 (m), 737 (m), 702 (m), 554 (m), 529 (m), 476 (w); 1H NMR (500 MHz, CDCl3): δ 7.56 - 7.52 (m, 4H), 7.47 (t, J = 8.2 Hz, 1H), 7.41 - 7.30 (m, 5H), 7.28 - 7.23 (m, 3H), 6.63 (s, 2H), 2.33 (s, 3H). 13C{1H} (126 MHz, CDCl3): δ 167.6, 161.1, 144.9, 137.3, 134.8, 132.5, 130.6, 130.6, 129.8, 126.7, 125.6, 124.7, 121.7, 121.5, 118.4, 118.0, 113.2, 20.1. HRMS (ESI+) m/z calcd for C28H18BF2N2O2 [M+H]+ 463.1429. Found 463.1438.

Synthesis of 24. According to GP3. 18 (25.0 mg, 0.04 O

H

mmol), Pd(OAc)2 (0.44 mg, 1.9 x 10-3 mmol, 0.05 equiv), PPh3 (1.0 mg, 3.9 x 10-3 mmol, 0.1 equiv), K2CO3 (16.2 mg, 0.12 mmol, 3 equiv) and toluene (4 mL). The

O

N N B F F 24

O

reaction mixture was stirred at 150 °C for 5 h. The crude was purified using 30% CHCl3/hexanes. The desired

product (12.5 mg, 0.03 mmol, 67% yield) was obtained as a golden solid. TLC (30% CHCl3/hexanes, Rf = 0.1); mp >300 °C dec.; IR (KBr, cm−1): 3116 (w), 3063 (w), 2971 (w), 2732 (w), 1705 (s), 1627 (s), 1557 (s), 1479 (s), 1450 (s), 1442 (s), 1415 (m), 1377 (s), 1355 (s), 1324 (m), 1292 (w), 1191 (w), 1161 (m), 1144 (s), 1118 (s), 1110 (s), 1013 (s), 992 (s), 820 (s), 810 (w), 751 (m), 697 (m), 557 (m); 1H NMR (500 MHz, CDCl3): δ 10.19 (s, 1H), 8.10 (d, J = 8.1 Hz, 2H), 7.83 (d, J = 8.0 Hz, 2H), 7.56 (t, J = 8.9 Hz, 4H), 7.35 (t, J = 8.5 Hz, 2H), 7.30 - 7.26 (m, 2H), 6.77 (s, 2H).

13C{1H}

(126 MHz, CDCl3): δ 191.5, 167.9,

161.2, 143.3, 139.2, 137.6, 134.2, 131.5, 129.8, 127.1, 124.9, 121.8, 121.3, 118.9, 118.2, 113.3. HRMS (ESI+) m/z calcd for C28H15BF2N2O3 [M]+ 476.1143. Found 476.1154.



Page 44 of 63

Synthesis of 25. According to GP3. 19 (20.0 mg, 0.03

OMe

mmol), Pd(OAc)2 (0.35 mg, 1.6 x 10-3 mmol, 0.05 equiv), PPh3 (0.82 mg, 3.1 x 10-3 mmol, 0.1 equiv),

O

N N B F F 25

K2CO3 (12.9 mg, 0.094 mmol, 3 equiv) and toluene (4 O

mL). The reaction mixture was stirred at 150 °C for 6 h.

The crude material was purified using 80% CHCl3/hexanes. The desired product (7.2 mg, 0.02 mmol, 48% yield) was obtained as a golden solid. TLC (20% THF/hexanes, Rf = 0.4); mp 297-299 °C; IR (KBr, cm−1): 2970 (w), 2926 (w), 2854 (w), 1735 (w), 1627 (w), 1605 (w), 1577 (s), 1478 (m), 1449 (s), 1442 (s), 1371 (s), 1356 (s), 1292 (m), 1252 (m), 1180 (w), 1159 (s), 1144 (s), 1114 (s), 1012 (m), 989 (s), 818 (m), 761 (w), 746 (w), 697 (w), 556 (w); 1H

NMR (500 MHz, CDCl3): δ 7.61 - 7.53 (m, 6H), 7.33 (t, J = 8.5 Hz, 2H), 7.29 - 7.26 (m,

2H), 7.10 (d, J = 8.6 Hz, 2H), 6.89 (s, 2H), 3.94 (s, 3H).

13C{1H}

(126 MHz, CDCl3): δ

167.2, 161.7, 161.0, 145.7, 134.5, 132.4, 126.6, 125.8, 124.7, 121.7, 121.6, 118.6, 118.1, 114.2, 113.2, 55.7. HRMS (ESI+) m/z calcd for C28H17BF2N2O3 [M]+ 478.1300, found 478.1322.

Synthesis of 26. According to GP3. 20 (30.0 mg, 0.05 mmol), Pd(OAc)2 (0.55 mg, 2.4 x 10-3 mmol, 0.05

O

N N B F F 26

equiv), PPh3 (1.3 mg, 4.9 x 10-3 mmol, 0.1 equiv), K2CO3 O

(20.4 mg, 0.15 mmol, 3 equiv) and toluene (4 mL). The reaction mixture was stirred at 150 °C for 6 h. The crude

material was purified using 60% CHCl3/hexanes. The desired product (15.9 mg, 0.03 mmol, 72% yield) was obtained as a golden solid. TLC (20% THF/hexanes, Rf = 0.4); mp >290 °C dec.; IR (KBr, cm−1): 2972 (w), 1628 (w), 1578 (s), 1478 (m), 1448 (s), 1345 (s), 1324 (s),


Page 45 of 63 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1292 (m), 1185 (w), 1159 (s), 1143 (s), 1108 (s), 1012 (w), 983 (s), 926 (w), 819 (s), 762 (w), 747 (w), 721 (m), 554 (m), 519 (w); 1H NMR (500 MHz, CDCl3): δ 7.66 - 7.54 (m, 9H), 7.34 (t, J = 8.5 Hz, 2H), 7.29 - 7.24 (m, 2H), 6.85 (s, 2H). 13C{1H} (126 MHz, CDCl3): δ 167.5, 161.1, 145.6, 134.6, 133.4, 130.8, 130.4, 128.6, 126.7, 124.7, 121.7, 121.6, 118.7, 118.3,113.2. HRMS (ESI+) m/z calcd for C27H16BF2N2O2 [M+H]+ 449.1272. Found 449.1271.

Synthesis of 27. According to GP2. 11 (30.0 mg, 0.05 mmol), p-fluorophenol (33.8 mg, 0.30 Br F

N N B O F F O 27

mmol), Na2CO3 (31.9 mg, 0.30 mmol) and

Br

acetonitrile (2.5 mL). The reaction mixture was F

stirred at 110 °C for 2 h. The crude material was

purified using 15% AcOEt/hexanes. The desired product (26.1 mg, 0.039 mmol, 79% yield) was obtained as red crystals. TLC (20% THF/hexanes, Rf = 0.55); mp 89-91 °C; IR (KBr, cm−1): 3121 (w), 2922 (w), 1564 (s), 1504 (s), 1491 (s), 1449 (s), 1351 (w), 1337 (w), 1252 (s), 1190 (s), 1175 (s), 1119 (s), 1033 (s), 1010 (s), 994 (s), 911 (m), 860 (m), 835 (m), 791 (m), 741 (m), 704 (m), 573 (w), 514 (w); 1H NMR (500 MHz, CDCl3): δ 7.46 - 7.42 (m, 1H), 7.36 - 7.27 (m, 3H), 7.13 - 7.07 (m, 4H), 7.05 - 7.00 (m, 4H), 6.69 (s, 2H), 2.29 (s, 3H). 13C {1H} (126 MHz, CDCl3): δ 160.7, 158.7, 158.1, 151.6, 151.5, 136.8, 131.8, 131.2, 130.8, 130.3, 130.2, 125.8, 119.6, 119.5, 116.5, 116.3, 95.9, 20.2. HRMS (ESI+) m/z calcd for C28H18BBr2F4N2O2 [M+H]+ 660.9745. Found 660.9772.

Synthesis of 28. According to GP2. 11 (30.0 Br HexO

Br N N B O F F O ACS Paragon Plus Environment OHex 28

mg,

0.05

mmol),

4-


(hexyloxy)phenol (58.5 mg, 0.30 mmol), Na2CO3 (31.9 mg, 0.30 mmol) and acetonitrile (2.5 mL). The reaction mixture was stirred at 110 °C for 2 h. The crude material was purified using 60% CHCl3/hexanes. The desired product (37.2 mg, 0.045 mmol, 90% yield) was obtained as red oil. TLC (15% DCM/hexanes, Rf = 0.90); IR (KBr, cm−1): 3694 (w), 2952 (s), 2929 (s), 2870 (s), 2858 (s), 1565 (s), 1493 (s), 1450 (s), 1350 (w), 1337 (w), 1295 (w), 1251 (s), 1213 (s), 1193 (s), 1178 (s), 1118 (s), 1033 (s), 1007 (m), 994 (m), 831 (m), 793 (w), 740 (m), 706 (m), 610 (w), 515 (w); 1H NMR (500 MHz, CDCl3): δ 7.42 (t, J = 8.8 Hz, 1H), 7.35 - 7.25 (m, 3H), 7.06 (d, J = 9.1 Hz, 4H), 6.83 (d, J = 9.1 Hz, 4H), 6.63 (s, 2H), 3.91 (t, J = 6.6 Hz, 4H), 2.28 (s, 3H), 1.79 - 1.71 (m, 4H), 1.50 - 1.40 (m, 4H), 1.37 - 1.27 (m, 8H), 0.90 (t, J = 6.9 Hz, 6h).

13C{1H}

(126 MHz, CDCl3): δ 158.4, 156.3, 149.3, 140.9,

136.9, 131.5, 131.5, 130.7, 130.3, 130.0, 127.8, 125.7, 119.3, 115.3, 95.5, 68.6, 31.7, 29.4, 25.8, 22.7, 20.2, 14.2. HRMS (ESI+) m/z calcd for C40H44BBr2F2N2O4 [M+H]+ 825.1714. Found 825.1730.

Synthesis of 29. According to GP2. 11 (30.0 mg, 0.05 mmol), 4-tert-butylphenol (45.2 Br

N N B O F F O 29

Br

mg, 0.30 mmol), Na2CO3 (31.9 mg, 0.30 mmol) and acetonitrile (2.5 mL). The reaction mixture was stirred at 110 °C for 1

h. The crude was purified using 15% THF/hexanes. The desired product (33.3 mg, 0.045 mmol, 90% yield) was obtained as red solid. TLC (20% THF/hexanes, Rf = 0.68); mp 108110 °C; IR (KBr, cm−1): 3681 (w), 2962 (m), 2864 (w), 1564 (m), 1494 (m), 1451 (s), 1364 (w), 1351 (w), 1334 (w), 1252 (s), 1215 (m), 1194 (m), 1120 (s), 1033 (s), 1013 (w), 830 (w), 741 (w), 699 (w), 549 (w); 1H NMR (500 MHz, CDCl3): δ 7.43 (t, J = 8.1 Hz, 1H), 7.36


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- 7.27 (m, 7H), 7.02 (d, J = 8.8 Hz, 4H), 6.67 (s, 2H), 2.30 (s, 3H), 1.29 (s, 18H). 13C{1H} (126 MHz, CDCl3): δ 158.2, 153.5, 147.5, 141.3, 136.9, 131.4, 131.3, 130.7, 130.3, 130.1, 128.0, 126.6, 125.7, 117.2, 96.3, 34.5, 31.6, 20.2. HRMS (ESI+) m/z calcd for C36H36BBr2F2N2O2 [M+H]+ 737.1188. Found 737.1203.

Synthesis of 30. According to GP2. 11 (30.0 mg, 0.05 mmol), 1-naphthol (28.9 mg, 0.20 mmol), Na2CO3 (21.3 Br

N N B O F F O 30

Br

mg, 0.20 mmol) and acetonitrile (2.5 mL). The reaction mixture was stirred at 110 °C for 1 h. The crude material was purified using 20% THF/hexanes. The desired product (29.3 mg, 0.040 mmol, 81% yield) was obtained

as purple solid. TLC (20% THF/hexanes, Rf = 0.3); mp 223-225 °C; IR (KBr, cm−1): 3673 (w), 3113 (w), 3055 (w), 1599 (w), 1560 (s), 1492 (s), 1455 (s), 1389 (s), 1349 (w), 1248 (s), 1223 (s), 1178 (m), 1132 (s), 1072 (s), 1044 (s), 1013 (s), 878 (m), 791 (w), 771 (m), 742 (m), 703 (m), 541 (w); 1H NMR (500 MHz, CDCl3): δ 8.33 - 8.31 (m, 2H), 7.86 - 7.82 (m, 2H), 7.65 (d, J = 8.3 Hz, 2H), 7.57 - 7.49 (m, 4H), 7.48 - 7.42 (m, 1H), 7.40 - 7.31 (m, 5H), 7.04 (d, J = 7.6 Hz, 2H), 6.72 (s, 2H), 2.36 (s, 3H). 13C{1H} (126 MHz, CDCl3): δ 158.4, 151.4, 141.3, 136.8, 134.6, 131.4, 131.3, 130.7, 130.2, 130.0, 128.0, 127.5, 126.9, 126.4, 125.6, 125.5, 125.2, 124.7, 121.9, 112.2, 95.7, 20.1. HRMS (ESI+) m/z calcd for C36H24BBr2F2N2O2 [M+H]+ 725.0249. Found 725.0267.



Synthesis of 31. According to GP2. 11 (30.0 mg, 0.05 mmol), 4-iodophenol (66.3 mg, 0.30 mmol, Br

N N B F O O F

I

31

6 equiv), Na2CO3 (31.9 mg, 0.30 mmol, 6 equiv)

Br I

and acetonitrile (2.5 mL). The reaction mixture was stirred at 110 °C for 2 h. The crude material

was purified using 10% THF/hexanes. The desired product (25.6 mg, 0.03 mmol, 58% yield) was obtained as red solid. TLC (20% THF/hexanes, Rf = 0.6); mp 106-107 °C; IR (KBr, cm−1): 3680 (w), 2972 (w), 1561 (s), 1496 (m), 1477 (s), 1448 (s), 1351 (w), 1336 (w), 1252 (s), 1216 (s), 1202 (s), 1186 (m), 1120 (s), 1033 (s), 1006 (s), 911 (w), 839 (w), 823 (w), 741 (w), 707 (w), 687 (w), 541 (w), 488 (w); 1H NMR (500 MHz, CDCl3): δ 7.63 (d, J = 8.9 Hz, 4H), 7.44 (t, J = 8.2 Hz, 1H), 7.37 - 7.26 (m, 3H), 6.87 (d, J = 8.9 Hz, 4H), 6.70 (s, 2H), 2.29 (s, 3H). 13C{1H} (126 MHz, CDCl3): δ 157.6, 155.6, 142.5, 138.8, 136.8, 131.7, 131.1, 130.9, 130.3, 130.3, 128.2, 125.8, 120.0, 96.4, 88.1, 20.3. HRMS (ESI+) m/z calcd for C28H18BBr2F2I2N2O2 [M+H]+ 876.7866. Found 876.7868.

Synthesis of 34. According to GP3. 27 (23.0 mg, 0.04 mmol), Pd(OAc)2 (0.39 mg, 1.7 x 10-3 mmol, F O

N N B F F 34

F O

0.05 equiv), PPh3 (0.91 mg, 3.5 x 10-3 mmol, 0.1 equiv), K2CO3 (14.4 mg, 0.104 mmol, 3 equiv) and toluene (4 mL). The reaction mixture was stirred

at 150 °C for 6 h. The crude material was purified using 60% CHCl3/hexanes. The desired product (13.3 mg, 0.03 mmol, 75%) was obtained as a golden solid. TLC (20% THF/hexanes, Rf = 0.6); mp >300 °C; IR (KBr, cm−1): 3401 (w), 2972 (w), 1635 (m), 1579 (s), 1474 (w), 1459 (m), 1374 (s), 1312 (s), 1265 (w), 1168 (w), 1137 (s), 1101 (s), 1072 (w), 993 (s), 966


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(m), 860 (w), 804 (w), 771 (w), 740 (w), 699 (w), 601 (w), 563 (w), 507 (w); 1H NMR (500 MHz, CDCl3): δ 7.50 - 7.45 (m, 3H), 7.41 - 7.33 (m, 3H), 7.22 (dd, J = 8.0, 2.7 Hz, 2H), 7.03 (td, J = 8.9, 2.7 Hz, 2H), 6.66 (s, 2H), 2.32 (s, 3H). 13C{1H} (126 MHz, CDCl3): δ 168.2, 161.0, 159.1, 156.9, 156.9, 145.9, 137.2, 135.0, 132.1, 130.7, 130.5, 130.0, 125.7, 122.5, 122.4, 118.8, 118.1, 113.8, 113.8, 113.7, 113.5, 108.5, 108.3, 20.1. HRMS (ESI+) m/z calcd for C28H16BF4N2O2 [M+H]+ 499.1240. Found 499.1238.

Synthesis of 35. According to GP3. 28 (40.0 mg, 0.05 mmol), Pd(OAc)2 (0.54 HexO O

N N B F F 35

OHex O

mg, 2.4 x 10-3 mmol, 0.05 equiv), PPh3 (1.3 mg, 4.8 x 10-3 mmol, 0.1 equiv), K2CO3 (20.1 mg, 0.15 mmol, 3 equiv) and

toluene (4 mL). The reaction mixture was stirred at 150 °C for 7 h. The crude material was purified using 40% CHCl3/hexanes. The desired product (22.3 mg, 0.03 mmol, 69%) was obtained as a golden solid. TLC (20% THF/hexanes, Rf = 0.7); mp 205-206 °C; IR (KBr, cm−1): 3066 (w), 2934 (m), 2868 (m), 1635 (m), 1577 (s), 1465 (s), 1460 (s), 1452 (s), 1415 (m), 1350 (s), 1316 (s), 1275 (s), 1207 (s), 1150 (s), 1106 (s), 993 (s), 965 (s), 945 (m), 871 (w), 858 (w), 828 (w), 778 (m), 742 (m), 701 (m), 691 (m), 580 (m), 494 (m); 1H NMR (500 MHz, CDCl3): δ 7.45 (t, J = 8.2 Hz, 1H), 7.42 - 7.31 ( m, 5H), 7.03 (d, J = 2.0 Hz, 2H), 6.85 (dd, J = 9.0, 2.6 Hz, 2H), 6.58 (s, 2H), 3.94 (t, J = 6.6 Hz, 4H), 2.32 (s, 3H), 1.85 - 1.71 (m, 4H), 1.49 - 1.41 (m, 4H), 1.39 - 1.25 (m, 8H), 0.9 (t, J = 7.0 Hz, 6H). 13C{1H} (126 MHz, CDCl3): δ 168.1, 156.6, 155.5, 144.6, 137.2, 134.7, 132.5, 130.6, 130.5, 129.7, 125.5, 122.0, 118.7, 117.8, 113.7, 113.4, 106.9, 69.0, 31.7, 29.4, 25.8, 22.7, 20.1, 14.2. HRMS (ESI+) m/z calcd for C40H42BF2N2O4 [M+H]+ 663.3207. Found 663.3194.



Synthesis of 36. According to GP3. 29 (26.0 mg, 0.04 mmol), Pd(OAc)2 (0.4 mg, 1.8 x 10-3

O

N N B F F 36

mmol, 0.05 equiv), PPh3 (0.9 mg, 3.5 x 10-3 O

mmol, 0.1 equiv), K2CO3 (14.6 mg, 0.11 mmol, 3 equiv) and toluene (4 mL). The

reaction mixture was stirred at 150 °C for 6 h. The crude material was purified using 60% CHCl3/hexanes. The desired product (13.0 mg, 0.02 mmol, 64% yield) was obtained as a golden solid. TLC (15% AcOEt/hexanes, Rf = 0.5); mp 250-252 °C; IR (KBr, cm−1): 3684 (w), 2960 (m), 2906 (m), 2868 (m), 1632 (m), 1575 (s), 1460 (s), 1404 (m), 1356 (s), 1342 (s), 1311 (m), 1291 (m), 1168 (s), 1124 (s), 1099 (s), 993 (s), 962 (m), 857 (w), 816 (s), 742 (w), 697 (m), 596 (w), 562 (w), 517 (w), 461 (w); 1H NMR (500 MHz, CDCl3): δ 7.55 (d, J = 2.0 Hz, 2H), 7.46 - 7.42 ( m, 3H), 7.41 - 7.30 (m, 5H), 6.61 (s, 2H), 2.33 (s, 3H), 1.34 (s, 18H). 13C{1H} (126 MHz, CDCl3): δ 167.9, 159.2, 147.9, 144.3, 137.3, 134.7, 132.6, 130.6, 130.5, 129.7, 125.5, 124.1, 121.1, 118.7, 118.5, 117.6, 112.3, 35.0, 31.8, 20.1. HRMS (ESI+) m/z calcd for C36H34BF2N2O2 [M+H]+ 575.2683. Found 575.2675.

Synthesis of 37. According to GP3. 30 (30.0 mg, 0.04 mmol), Pd(OAc)2 (0.5 mg, 2.07 x 10-3 mmol, 0.05 equiv), PPh3 (1.1 mg, 4.1 x 10-3 mmol, 0.1 O

N N B F F 37

O

equiv), K2CO3 (17.2 mg, 0.12 mmol, 3 equiv) and toluene (4 mL). The reaction mixture was stirred

at 150 °C for 7 h. The crude material was purified using 30% CHCl3/hexanes. The desired product (8.4 mg, 0.01 mmol, 36% yield) was obtained as golden crystals. TLC (60%


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CHCl3/hexanes, Rf = 0.4); mp >300 °C; IR (KBr, cm−1): 3058 (w), 2970 (w), 1639 (w), 1606 (m), 1580 (s), 1558 (m), 1461 (m), 1438 (m), 1390 (s), 1373 (s), 1357 (s), 1335 (s), 1279 (m), 1262 (m), 1144 (s), 1131 (s), 1026 (s), 1005 (s), 965 (s), 847 (m), 803 (m), 736 (m), 696 (m), 671 (w), 602 (w), 582 (w), 560 (w), 503 (w), 457 (w); 1H NMR (500 MHz, CDCl3): δ 8.42 (d, J = 8.3 Hz, 2H), 7.92 (d, J = 8.2 Hz, 2H), 7.72 (d, J = 8.4 Hz, 2H) 7.68 - 7.60 ( m, 4H), 7.54 (t, J = 8.0 Hz, 2H), 7.49 (t, J = 8.2 Hz, 1H), 7.45 (d, J = 6.6 Hz, 1H), 7.43 - 7.34 (m, 2H), 6.67 (s, 2H), 2.37 (s, 3H). 13C{1H} (126 MHz, CDCl3): δ 167.5, 156.6, 145.3, 137.3, 135.1, 132.8, 132.6, 130.7, 130.6, 129.8, 128.5, 127.3, 126.4, 125.6, 125.1, 121.8, 120.9, 119.5, 119.1, 117.3, 116.9, 20.2. HRMS (ESI+) m/z calcd for C36H21BF2N2O2K [M+K]+ 601.1302. Found 601.1288.

Synthesis

OMe

of

39.

According to GP2. 13 O O H3CO O

NH

Br

N N B F O O F 39

Br

(30.0 mg, 0.05 mmol), N-

O HN

O OCH3 O

(tert-butoxycarbonyl)-Ltyrosine methyl ester (86.6 mg, 0.29 mmol, 6 equiv),

Na2CO3 (31.1 mg, 0.29 mmol, 6 equiv) and acetonitrile (2.5 mL). The reaction mixture was stirred at 110 °C for 1 h. The crude material was purified using 20% acetone/hexanes. The desired product (36.0 mg, 0.034 mmol, 71% yield) was obtained as a red solid. TLC (20% acetone/hexanes, Rf = 0.9); mp 106-108 °C; IR (KBr, cm−1): 3666 (w), 2975 (w), 1743 (m), 1713 (s), 1605 (w), 1575 (m), 1555 (m), 1510 (m), 1492 (s), 1450 (s), 1366 (w), 1350 (w), 1255 (s), 1209 (m), 1179 (m), 1164 (m), 1127 (s), 1037 (m), 1016 (m), 993 (w), 854 (w), 835 (w), 760 (w), 706 (w); 1H NMR (500 MHz, CDCl3): δ 7.49 (d, J = 8.7 Hz, 2H), 7.10 - 7.00



Page 52 of 63

(m, 10H), 6.94 (s, 2H), 4.94 (d, J = 8.1 Hz, 2H), 4.54 (dd, J = 13.7, 6.1 Hz, 2H), 3.91 (s, 3H), 3.65 (s, 6H), 3.10 - 2.99 (m, 4H), 1.41 (s, 18H). 13C{1H} (126 MHz, CDCl3): δ 172.3, 162.2, 157.6, 155.2, 154.9, 142.4, 132.4, 132.2, 132.0, 130.6, 127.5, 124.6, 118.0, 114.5, 95.8, 80.1, 55.7, 54.6, 52.3, 37.8, 28.4. HRMS (ESI+) m/z calcd for C46H50BBr2F2N4O11 [M+H]+ 1043.1891. Found 1043.1884. Synthesis of 40. According OMe

to GP2. 13 (30.0 mg, 0.05 mmol), estrone (79.3 mg,

Br

O

H H

H

N N B F O O F 40

0.29

Br

mmol,

6

equiv),

Na2CO3 (31.1 mg, 0.29 H

H H

O

mmol,

6

equiv)

and

acetonitrile (2.5 mL). The

reaction mixture was stirred at 110 °C for 1 h. The crude material was purified using 40% AcOEt/hexanes. The desired product (34.0 mg, 0.034 mmol, 70% yield) was obtained as a red solid. TLC (40% acetone/hexanes, Rf = 0.2); mp 180-182 °C; IR (KBr, cm−1): 2929 (s), 2862 (s), 1738 (s), 1605 (s), 1576 (s), 1554 (s), 1487 (s), 1450 (s), 1349 (m), 1297 (w), 1252 (s), 1225 (s), 1202 (s), 1179 (s), 1123 (s), 1036 (s), 993 (m), 928 (m), 913 (s), 837 (w), 819 (w), 792 (w), 763 (w), 732 (w), 707 (w), 634 (w), 548 (w); 1H NMR (500 MHz, CDCl3): δ 7.50 (d, J = 7.8 Hz, 2H), 7.20 (d, J = 8.5 Hz, 2H), 7.06 (d, J = 7.8 Hz, 2H), 6.95 (s, 2H), 6.85 - 6.79 (m, 4H), 3.92 (s, 3H), 2.86 (d, J = 5.2 Hz, 4H), 2.50 (dd, J = 19.1, 8.7 Hz, 2H), 2.40 2.33 (m, 2H), 2.29 - 2.22 (m, 2H), 2.18 - 2.09 (m, 2H), 2.07 - 1.91 (m, 6H), 1.69 - 1.37 (m, 15H), 0.91 (s, 6H). 13C{1H} (126 MHz, CDCl3): δ 220.9, 162.1, 157.6, 153.9, 142.2, 138.3, 135.8, 132.2, 131.8, 127.6, 126.6, 124.8, 117.4, 114.7, 114.4, 96.2, 55.7, 50.6, 48.1, 44.2,


Page 53 of 63 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


38.2, 36.0, 31.7, 29.6, 26.5, 25.9, 21.7, 14.0. HRMS (ESI+) m/z calcd for C52H52BBr2F2N2O5 [M+H]+ 993.2293. Found 993.2271.

Synthesis of 41. According to

OMe MeO

BocHN

NHBoc

O

Pd(OAc)2 (0.4 mg, 1.68 x 10-3

O

N O

N B F F

GP3. 39 (35.0 mg, 0.03 mmol),

OMe

mmol, 0.05 equiv), PPh3 (0.9

O

mg, 3.4 x 10-3 mmol, 0.1

41

equiv), K2CO3 (24.0 mg, 0.10

mmol, 3 equiv) and toluene (4 mL). The reaction mixture was stirred at 150 °C for 6 h. The crude material was purified using 35% acetone/hexanes. The desired product (20.0 mg, 0.02 mmol, 68% yield) was obtained as a dark blue solid. TLC (40% acetone/hexanes, Rf = 0.5); mp 144-146 °C; IR (KBr, cm−1): 3351 (w), 2975 (w), 1739 (m), 1715 (m), 1694 (m), 1605 (m), 1577 (s), 1525 (w), 1510 (w), 1497 (w), 1468 (m), 1459 (m), 1416 (w), 1360 (s), 1293 (m), 1255 (m), 1159 (s), 1111 (s), 1001 (s), 860 (w), 814 (w), 801 (w), 754 (w), 721 (w), 699 (w), 558 (w), 528 (w); 1H NMR (500 MHz, CDCl3): δ 7.59 (d, J = 8.7 Hz, 2H), 7.46 (d, J = 8.4 Hz, 2H), 7.37 (d, J = 1.6 Hz, 2H) 7.13 - 7.06 ( m, 4H), 6.87 (s, 2H), 5.01 (d, J = 8.0 Hz, 2H), 4.60 (dd, J = 12.3, 5.6 Hz, 2H), 3.95 (s, 3H), 3.69 (s, 6H), 3.22 - 3.06 (m, 4H), 1.40 (s, 18H). 13C{1H} (126 MHz, CDCl3): δ 172.4, 167.4, 161.8, 160.1, 155.2, 145.8, 134.5, 132.8, 132.5, 127.6, 125.7, 122.2, 121.9, 118.7, 117.9, 114.2, 113.0, 80.2, 55.7, 54.8, 52.5, 38.6, 28.4. HRMS (ESI+) m/z calcd for C46H48BF2N4O11 [M+H]+ 881.3383. Found 881.3378. OMe

Synthesis of 42. According to O

O H

H H

H

O

N N H H F B FACS O Paragon Plus Environment 42

GP3. 40 (32.0 mg, 0.03 mmol),


Pd(OAc)2 (0.4 mg, 1.61 x 10-3 mmol, 0.05 equiv), PPh3 (0.8 mg, 3.2 x 10-3 mmol, 0.1 equiv), K2CO3 (13.4 mg, 0.10 mmol, 3 equiv) and toluene (4 mL). The reaction mixture was stirred at 150 °C for 6 h. The crude material was purified using 60% CHCl3/hexanes. The desired product (9.1 mg, 0.01 mmol, 34% yield) was obtained as a blue solid. TLC (50% acetone/hexanes, Rf = 0.6); mp >300 °C decompose; IR (KBr, cm−1): 2930 (w), 2864 (w), 1738 (m), 1606 (w), 1574 (m), 1454 (m), 1417 (w), 1362 (s), 1338 (s), 1289 (m), 1254 (w), 1183 (m), 1114 (s), 996 (m), 983 (s), 974 (s), 906 (w), 892 (w), 877 (w), 758 (w), 737 (w), 702 (w), 666 (w), 583 (w); 1H NMR (500 MHz, CD2Cl2-CDCl3): δ 7.61 (d, J = 8.4 Hz, 2H), 7.56 (s, 2H), 7.27 (s, 2H), 7.11 (d, J = 8.4 Hz, 2H), 6.85 (s, 2H), 3.94 (s, 3H), 3.07 - 3.01 (m, 4H), 2.52 - 2.32 (m, 6H), 2.18 - 2.02 (m, 7H), 2.02 - 1.88 (m, 3H), 1.69 - 1.57 (m, 6H), 1.56 - 1.39 (m, 6H), 0.91 (s, 6H).

13C{1H}

(126 MHz, CD2Cl2-CDCl3): δ 221.0, 167.9, 162.2,

160.0, 145.4, 137.4, 136.9, 134.8, 133.0, 126.3, 119.8, 118.9, 118.7, 118.3, 114.6, 113.1, 56.2, 51.2, 48.5, 45.0, 38.7, 36.5, 32.3, 30.9, 27.0, 26.8, 22.2, 14.4. HRMS (ESI+) m/z calcd for C52H50BF2N2O5 [M+H]+ 831.3784. Found 831.3773.

Supporting information: 1H

and 13C NMR spectra of the compounds prepared. . Absorption and fluorescence spectra.

Cyclic voltammograms. Correlation of the fluorescence efficiency with solvent scales. Photophysical and laser data. Crystallographic data by X-ray diffraction. XYZ coordinates and energies of the simulated geometries. The Supporting Information is available free of charge on the ACS Publications website at DOI: xxxxx


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Author information: Corresponding Author: *Email: [email protected], [email protected] ORCID Eduardo Peña-Cabrera: 0000-0002-2069-6178 José L. Belmonte-Vázquez: 0000-0002-1052-5260 Edurne Avellanal-Zaballa: 0000-0002-5218-3764 Ernesto Enríquez-Palacios 0000-0001-7270-2544 Luis Cerdán: 0000-0002-7174-2453 Ixone Esnal: 0000-0001-9625-6876 Jorge Bañuelos: 0000-0002-8444-4383 Clarisa Villegas-Gómez: 0000-0003-3221-1809 Iñigo López Arbeloa: 0000-0002-8440-6600

Notes The authors declare no competing financial interest. Acknowledgements We gratefully acknowledge the Spanish Ministerio de Economia y Competitividad (MAT2017-83856-C3-3-P) and Gobierno Vasco (project IT912-16) for financial support. E. A.-Z. thanks also Gobierno Vasco for a predoctoral fellowship. The authors thank SGIker of UPV/EHU for technical and human support with the X-ray diffraction measurements and computational calculations, which were carried out in the “arina” informatic cluster. J.L.B.V. and E.E.-P. thank CONACyT for scholarships. CONACyT (grants 253623, 123732) is acknowledged.

Donation

of

8-methylthioBODIPY

(www.cuantico.mx) is appreciated.


by

Cuantico

de

Mexico


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(25) Jiao, L.; Yu, C.; Liu, M.; Wu, Y.; Cong, K.; Meng, T.; Wang, Y.; Hao, E. Synthesis and Functionalization of Asymmetrical Benzo-Fused BODIPY Dyes. J. Org. Chem. 2010, 75, 6035–6038. (26) Okujima, T.; Tomimori, Y.; Nakamura, J.; Yamada, H.; Uno, H.; Ono, N. Synthesis of -Expanded BODIPYs and Their Fluorescent Properties in the Visible-near-infrared Region. Tetrahedron 2010, 66, 6895-6900. (27) Heyer, E.; Retailleau, P.; Ziessel, R. α-Fused Dithienyl BODIPYs Synthesized by Oxidative Ring Closure. Org. Lett. 2014, 16, 2330-2333. (28) Hayashi, Y.; Obata, N.; Tamaru, M.; Yamaguchi, S.; Matsuo, Y.; Saeki, A.; Seki, S.; Kureishi, Y.; Saito, S.; Yamaguchi, S.; Shinokubo, H. Facile Synthesis of Biphenyl-Fused BODIPY and Its Property. Org. Lett.2012, 14, 866-869. (29) Kubo, Y.; Minowa, Y.; Shoda, T.; Takeshita, K. Synthesis of a New Type of Dibenzopyrromethene-boron

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(38) Isomer 3 was prepared in two steps; the first arylation reaction took place in refluxing dioxane for 96 h, while the second arylation took place in refluxing toluene for 48 h (see ref. 32). (39) Chen, J.; Burghart, A.; Derecskei-Kovacs, A.; Burgess, K. 4,4-Difluoro-4-bora-3a,4adiaza-s-indacene (BODIPY) Dyes Modified for Extended Conjugation and Restricted Bond Rotations. J. Org. Chem. 2000, 65, 2900–2906. (40) Kee, H. L.; Kirmaier, C.; Yu, L.; Thamyongkit, P.; Youngblood, W. J.; Calder, M. E.; Ramos, L.; Noll, B. C.; Bocian, D. F.; Scheidt, W. R.; Birge, R. R.; Lindsey, J. S.; Holten, D. Structural Control of the Photodynamics of Boron-Dipyrrin Complexes. J. Phys. Chem. B 2005, 109, 20433-20443. (41) Luo, L.; Wu, D.; Li, W.; Zhang, S.; Ma, Y.; Yan, S.; You, J. Regioselective Decarboxylative Direct C–H Arylation of Boron Dipyrromethenes (BODIPYs) at 2,6Positions: A Facile Access to a Diversity-Oriented BODIPY Library. Org. Lett. 2014, 16, 6080-6083. (42) Reichardt, C. Solvatochromic Dyes as Solvent Polarity Indicators. Chem. Rev. 1994, 94, 2319-2358. (43) García-Moreno, I., Costela, A., Martín, V. Pintado-Sierra, M., Sastre, R. Materials for a Reliable Solid-state Dye Laser at the Red Spectral Edge. Adv. Funct. Mater. 2009, 19, 25472552. (44) Durán-Sampedro, G.; Agarrabeitia, A. R.; Cerdán, L.; Pérez-Ojeda, M. E.; Costela, A.; García-Moreno, I.; Esnal, I., Bañuelos, J.; López-Arbeloa, I.; Ortiz, M. J. Carboxylates vs Fluorines: Boosting the Emission Properties of Commercial BODIPYs in Liquid and Solid Media. Adv. Funct. Mater. 2013, 23, 4195-4205.



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Synthetic Approach to Readily Accessible Benzofuran-Fused BODIPY

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